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Exploring the Steel-Spring'ed EMS powerplant

2/26/2025

Using a 34k in 0.20" cal

The EMS powerplant is a peculiar beast.

The result of extensive tests (thousands and thousands of shots taken), and the desire to make a dual power-plant rifle, it is a 7 part system (L to R in the picture below):

Piston
Forward guide
Spring
Shim
Rear guide
Piston skirt centering bell
Filler Screw

Now, being a 7 part system means TWO things:
1.- More manufacturing cost
2.- The need for more precision in the execution

For three years now, the "Motto" of the DIANA brand has been:
"Our Mission is Precision"

AND, as it is basically unavoidable, like all changes, it needs to start from within (remember the song "The Man in Mirror"?)

So, this exploration goes into what can be GAINED by using a steel spring in the D-34 sized break-barrels with the EMS architecture, and what needs to be changed.

Let's start with the diagram:

Numbers 1, 2, 3, and 4 are the basic mechanisms tube with the trigger block included.
Number 5 is the rear spring guide
Number 6 is a steel centering "bell" designed to hold the piston in the center when cocked, and allow the interference sear to do its job consistently.
Number 7 is a washer to protect the plastic rear guide from the steel spring
Number 8 is the screw that affixes the centering bell (# 6) to the trigger block (#2).
Number 9 is the spring itself
Number 10 is the front guide that telescopes into the rear guide
and Number 11 is the piston

Now, let us think about DIANA's "motto":
We have 7 pieces that need to align along an axis that is about a foot long (12"~~ 300 mm) and upon whose precision depends the consistency and efficiency of the powerplant.

¿Why?

Well, in a spring-piston powerplant there are several energy "sinkholes". The most important is friction, we take care of that mostly through lubrication. The next one in importance is "chatter", and that means all the small lateral movements that happen when a long thing vibrates along an expansion stroke.

How important is chatter?

Well, let's just say that IN THE SAME rifle-pellet-lubricant combination, a traditional D34 powerplant was able to yield about 13½ ft-lbs
Then, with the NTec unit (that prevented a lot of the chatter), yield went up to 16 ft-lbs.
With a "precisioneered" (precision engineered) EMS architecture it is now yielding 17 to 17½ ft-lbs
AND with a reduced cocking effort because Gas Springs will ALWAYS start from a very high force and go higher from there.

So, by reducing the tolerances and ensuring that everything is operating along the same axis, we gained a bit more than 25% yield with a reduction of about 20% in the cocking effort (and therefore the energy input into the system).

Yup! That is what true precision gains for us.

If you put it in numbers:

Efficiency of a traditional 34 PP.-
13.6 kg (30 #F, or 133.4 N) PCF over 135° of arc (2.36 Rads) on a 0.34 m radius.- Since the Compression starts from a value (preload), we will take that into account by an arbitrary/empirical factor of 0.6 (the average is a little more than ½ the peak) That means 64.22 Joules of energy input, vs. 17.6 J output, means an efficiency of about 27%

Efficiency of an Ntec equipped version:
20 kg (44 #F, or 196.2 N) PCF over the same arc and radius, means a peak input of 157 J, since the NTec starts from a substantially higher force, the factor now for the average force is about 0.7, instead of 0.6, so the input is 110.2 J, for an output of 21.7 J, that means an efficiency of 20%

Efficiency of the steel spring'ed EMS PP.- you need to input 18.2 kg (40 #F or 178.2 N)since this PP starts from a low value, we use again the 0.6 factor for the average vs the peak, and that means an input of 85.8 J, for an output of 24 J means an efficiency of 28%

Is this performance max'ed out for the 34 size? Yes. To get more/more efficiency, we would need to go the route of the fixed barrels.

Now, is there a way to achieve these gains without increasing the cost?

Well, yes, but it needs a change of thinking.

On one hand, parts #'s 5, 6, 7 and 8 can be "unitized" in a single piece made up with two different materials in three parts.
Could it be made as a single extrusion/molding? Perhaps. Modern moulding techniques do allow for "overmoulding", meaning that you mould a part, then insert that into another mould and the final injection takes place.

But what is a dramatic departure from the traditional method of manufacturing is that this "unitized" part would have to be made OVERSIZE, and then CNC machined to precise dimensions with small tolerances.

The frontal guide (#10) also needs a serious tightening of tolerances, especially at the front where it meets the piston. AND the fit between the OD of the "stem" of part #10 and the ID of the "Unitized" guide also needs serious tightening, as well as the fit between spring and guide.

I am now hearing all of you saying:"Precision in manufacturing is not the same as precision at the target

LOL!

Yes, that is true, and not only precision, but accuracy is also important. Theoreticians think that if you achieve precision, then accuracy is the "simple matter of adjusting the sights".
Alas, those shooters with experience know that this is an oversimplification.

What happens if the sights don't adjust consistently?
What happens if the sights are vulnerable to thermal differences?
What happens if the sights are simply not adequate to the target at hand?

Many of the problems are "solved" using a scope, but scopes have their own issues, especially in the field.

Still, the best procedure to test a rifle is by shooting it.

And, yes we did a ton of that, mainly because our scope suddenly started playing scope "games" on us. We would shoot a great group at some point in the target, then the next group would be elsewhere. The we shot a shotgun pattern that was not even a group!
Since that particular scope has been with me for a LONG time and never failed, AND that scope has been mounted in "accurized" ZR Mounts, that is the last point we suspected.
So, we tuned the bedding (after all, even the most "sophisticated 34 is still a 34.We tuned the Muzzle piece (an HPM Unit), and we tested different pellets.

The pellets were not the issue, the JSB's 13.7's were shooting as they should.
The bedding took a bit of experimenting, at this power level, minute differences have substantial effects.
After three days of testing (and two full pages like this), we decided something was wrong, this is what we were getting:

Yes there were some great groups, but... no consistency.
This is a good example:

Five shots vertically scattered, then a tight group, then another five horizontally scattered.

Now look at this:

Top row left to right:
A so-so group, then a better group, then a hideous group, then another good group with a lonely "flyer".

AND, we knew that it was not a question of oscillating MV's:

So, we decided to swap scopes.
Wonder of wonders, miracle of miracles! LOL!
This is what we got, straight off the bat:

This is the process of sighting in.

And when you click an inexpensive scope, you EXPECT to have to take one or two shots to settle it down.
Even some not so inexpensive scopes do this. Especially in a springer that is yielding almost twice its own weight in output energy.

At 25 yards, these are dime-sized groups from the knee and a scope @ 9X, let's validate that assertion:

Yes, I know there is one Canadian dime there, What do you want? I like the guys!

Want to see how the groups are totally covered?

I need to finish the sighting in, but that will come at a later date when there is less wind.

Is it easy to shoot a light and powerful break barrel? Nope!

It would make a heck of a hunting rifle, or perhaps Silhouette?. Short, light (9# WITH scope), and with a lot of KO power as far as pigeons, squirrels, grackles , rats, etc. are concerned.

So, there you have it. Power, precision and accuracy in one small, light package.

AH! before I forget, dry lubed. Absolutely no oils or greases in the compression section.

In short, precision at the target comes from "internal harmony", and "internal harmony" comes from the precision fit between the parts that make up the heart and soul of the airgun.

Same could be said of humans ¿no?

Keep well and shoot straight!

HM

0 Comments

Playing a little with a DIANA 58

2/6/2025

9 Comments

Re-sighting it really, LOL!

One of the pleasures of the professional airgunsmith is that, at times, someone, somewhere, finds something completely unusual and "out of this world", LOL!
This is one of those occasions.
A friend told me he had just acquired "an old DIANA", and that he wanted me to have a "looksie".
Well, we met at our Monday Night shoots and I was taken aback when the old dame came out of the case.
A REALLY OLD DIANA!
I thought to myself: "this is probably the first model to come out with a forearm in the stock"
Well, it seems I was not too off the mark.
After all the admiration, my friend told me that the gun was shooting to the right and up, he had to aim at the lower left corner of the target to hit the bullseye.
Hmmmm, that's not good.
Further, he told me that the sights had no way of adjusting the windage. Hmmmmmm
So, after looking in detail at the rifle, it was clear that the design intention had been to drift the sights to set the windage. The blade had a way to elevate, though a bit primitive, it was used all the way into the year 2k in the DIANA 30 (the shooting gallery/Kermesse gun).
So, that's where that peculiar sight came from!
After a few more words were exchanged, we concentrated on the task at hand (shoot 60 "for score" shots) and once that was done, we all had a long session of shooting the breeze.

When I got home, I put away the gun and during the week, in one of those instants where it seems time has stopped because you are waiting for materials, parts, tools, or "all of the above" to arrive I decided to tackle the "simple" job of re-sighting in the old lady.

In the light of the workshop, daytime, and more awake, I came to realize that for a gun that old it was in amazing state of preservation. Bluing, wood finish, everything was almost pristine.

BUT! Enough words, let's take a look at some pictures:

The DIANA 58 in all its splendor

Which is vastly superior to what they offered in the catalog:

There are some small differences, like the ring front sight that is not in the actual sample, and the "handle" of the cocking lever that disappeared, but apart from that it is a proper incarnation of the line drawing.
The "branding" in those days was a bit "Spartan" (or should we say "Laconic"?):

No model, no manufacturer, no origin.
Still, simple, elegant, and very clearly legible.
BTW, the rifle has NO OTHER markings.

This is the rear sight:

As you can clearly see the dovetail allows for some drifting and the elevation blade runs on the head of the screw. Not a "micrometer visier" but quite serviceable.
There are range markings on the side of this sight (10 to 50, I assume, meters), though not particularly exact/correct, it is a tribute to how something simple can still be effective.
And this is the front sight:

Again "driftable" in the dovetail.

After a few test targets and some measurements, the results were quite satisfactoyry and I had time to admire the craftsmanship that went into this rifle. Let's look into it in some detail:

This is where the cocking lever connects to the linkage.
The main screw has a "fixation" screw that can lock the position of the screw every ½ turn. And we need to assume that the axle screw is a "Shoulder screw". Nowadays, the same job is performed by a pin, with or without a head, and one or two E-Clips.
Now, let's move forward a little. This is the lever:

And, if we look at it in detail, we see that it was milled, and even checkered, from solid:

Now let's move back and see how the lever/linkage arrangement gets connected to the mechanisms tube AND at the same time serves as a mounting platform for the tap to load the pellets:

Also note above the distance markings of the rear sight.

In the purest sense of the word in gunsmithing, THIS would be the "receiver ring" because at the front, it receives the barrel and the rear, receives the power source.

Now, we go all the way to the back of the mechanics and we find this:

A cocking knob!

That cocked looks like this:

Because, after you have cocked the spring, and inserted the pellet into the tap, you still have to cock the hammer that strikes the sear that releases the spring.
Safety? Or a simple solution to holding about 200 # of force and releasing them with a gentle trigger squeeze?
¿Both?
We'll never know. It makes the loading cycle complicated, but safe and the trigger pull more than manageable for some precision shooting.

If we go to the stock now and look at the forend:

We find finely grained walnut, well sculpted for the purpose (this is one of those guns where the artillery hold is absolutely indispensable!
And screw cups! If anyone thought it was a modern invention, here is the proof that in the world of guns, there is VERY LITTLE that is truly original and new.

AND, what can we say about the pistol grip?
Extremely "English" in its conception and execution:

Rounded heel, flattened diamonds, double borderline. This pistol grip would be perfectly at home in any high end English Side X Side of the times.

The one "problematic" are this rifle has is where someone (surely an American), decided to use a "tang sight" to shoot longer ranges with more precision than the OEM sights allowed:

According to my measurements, these holes can receive exactly the base of a Sharps/Borchardt long range rifle.
Still available, it is not out of the question to get the bases and then add a mid-range sight that would allow the shooter to shoot out to 65-75 yards.
Since the rifle is a 5.5 mm's ("number 2 bore" per the English nomenclature of the time) / 0.22" it is capable of reaching the 55 yards with enough authority to drop the Rams.

Going all the way to the back, the buttplate is a steel plate:

And again the complete gun:

Shooting a round of 10M MMS (Mexican Metallic Silhouettes), I achieved a 32/40, not a stellar score, and just slightly under the score I would have shot with the K98 S but then the K98 S easily has one of the best sets of notch and bead iron sights in modern airguns ever, and that includes the FWB Sport of modern times.

Point is that the gun is now shooting to POA without any need to do anything to the barrel and using fairly inexpensive Crosman Copperhead Pointed pellets and more reliable/consistent JSB's Express.

All in all a VERY enjoyable excursion through a time machine.

Would it be possible to make an airgun like this today?

Yes, issue here is :
Would anyone buy it at the cost it would imply?

Just taking a SWAG of what a gun like this would cost today: It would run north of $2,500 MSRP. Even using modern CNC machinery and current metals.

Hope you have enjoyed the pictures as much as I enjoyed having that old lady for a short while.

Keep well and shoot straight!

HM

9 Comments

The Hämmerli Pneuma

1/14/2025

2 Comments

Disclaimer:
Modifications made to this rifle were performed by an experienced professional airgunsmith. And, proved safe in THIS gun.
No warranties are implied nor extended.
We have no control of what you do on your own.
If you do decide to make ANY modification to a PCP, be conscious of which elements are under pressure and realize that, even 10 BAR's CAN cause SERIOUS bodily harm.
These modifications have not been reviewed, nor approved by Hatsan or Walther/Hämmerli
Again: Be careful! You are the only guardian of your health and safety.

Phewwwwww!

OK, now with the "small print" done, let's get down to our matter.

What is, exactly a "Hämmerli Pneuma"?

The short answer is that a Hämmerli Pneuma is just a re-branded Hatsan AT44

The long answer is that, for ME, there is NOTHING of "Hämmerli" in this rifle, and to get what I mean by this, we have to go back more than just a few decades.
Many years ago (58, to be precise), I had the luck to see my first Match rifle.
Walking to my nearest "Sears Roebuck de México SA de RL y CV" (the Mexican Version of the company), I was regaled with the sight of the most beautiful rifle I had ever seen.
It was a Hämmerli Mod 45 Free Rifle.
Priced at the, then, EXORBITANT cost of Mx$3,595 (1966's US$ 287 ) it was way beyond the wildest dreams of a 10 years old.
Something like this:

Years later, I would come to own an Anschütz Match 64, and a Tanner Free 300 M, plus a Steyr SSG '69. But I can certainly say that my love affair with precision target rifles was born at the old "Sears" in Mexico City.

Therefore I always had a soft spot for the brand.

When UMAREX purchased Walther and Hämmerli I was dismayed.

What was going to happen?

Well, now, even that is history.

Luckily for Walther, the "Match" branch was spun off as an independent unit and they still produce top notch airguns, The Firearms branch is also independent, having been set apart from the UMAREX deal.
The Walther "Sport" branch of the airgun business produced two of the most advanced spring-piston airguns in history, only to die a quick death with the sale of all the parts and stock of what remained of the Walther Century Varmint parts to UMAREX for the creation of their 3400 model.

On its side, the Hämmerli brand has graced products made in China, Turkey and Mexico. Products that whether spring-piston or PCP power plant, have little to do with the Precision Match rifles of yesteryear.

Nowadays, through the German connection (Hämmerli was a SWISS company), they are re-branding the ISSC SPA "toggle bolt" RF as the Hämmerli Sport, and that is a gun that MAY be worthy of the brand, if the quality of the barrels honor the precision they promise. It should be noted that it is the THIRD "re-birth" of this particular RF.
BUT, we're getting away from the "Pneuma"

And here we arrive at the short answer: when UMAREX wanted a Hämmerli branded PCP that would get some traction in the "Sport" section of PCP airguns (they had already developed the Match version of their bottom of the line Walther into a passable beginner Match gun) they picked Hatsan, and the Pneuma is the result of re-branding a Hatsan AT-44.

The AT-44 has in itself, gone through at least two versions, the original one that we will call the "old model", and the new one that is sold under the "H" spec.
When Hämmerli discontinued the Pneuma, Hatsan advanced with the "H" version and the way the tanks hold the valve changed a little. This will be important later on.

Soooooooo....

When a very good friend of mine asked me if I would take a look at his son's airgun, I replied that it all depended on the gun, I asked what needed to be looked into, and he commented that they could not get more than 20 shots out of a full tank fill and that they wanted to have the gun regulated, so that they could plink in a more comfy environment where the gun didn't need constant re-airing.

I answered that, subject to the availability of spare parts and accessories, I would be glad.

The Project

Everything started then at one of our Monday night shoots where, and when, I received a huge case with a smallish PCP.
I checked it over and wondered exactly what had I gotten myself into. LOL!

Some online research clarified to me that it was a Hatsan. Checked with my friends at Altaros (best regulators out there), and they DID have a regulator for the Hatsan. The only issue was winter holiday season in Europe was starting and all means of transportation were getting overloaded.
I still decided to order one because that would be the "gold standard" by which to judge other options.

Almost at the same time, I found the Hatsan made regulators and some looking into the old Youtube videos provided some interesting information:
a) there were two types of valves at the tanks. One that uses a simple plastic plug to hold the valve return spring (what we call the old model), and another (H type) that actually has a plastic screw in perforated plate that holds a much stronger return spring.
b) the inside finish of the tanks had gone down over the years. The older tanks were much more even and smoother
c) the regulator for the older model had a relatively small "plenum", which would limit the tuning options
So, I ordered a new tank under the new "H" spec and ordered two "H" regulators.
d) what I liked a LOT, was that the valve was IN THE TANK.

When the regulators arrived, to my dislike, it turned out that the newer "H" regulators were non-vented.

I generally like vented regulators for all guns, the non-vented regulators have a tendency to "creep" and even if it is well made enough that they do not "creep", the first shot is always low.
In a hunting scenario this will surely cause a problem, either a miss or, worse, a bad hit that will not cause immediate death. That is, ethically, unacceptable and should be avoided.
So, some non-vented regulators do require one to three "evening out" shots prior to actually starting the hunt, and then, the hunter should know how long the reg can stay under working conditions.
Not hard to determine, but something that needs to be determined BEFORE.

In view of that condition, and after studying what we had at hand, I decided to modify one of the "H" regulators to be a vented one.

They may look the same (well, almost), but the working is a bit different.
Let's see them from the front:

On the left is the vented one, on the right the OEM one.
observe where the "dimple" has been lathe turned in the center.
And now, let's look at the OEM one's attachment method:

As you can see, the valve return spring is held in place and pre-compressed by the regulator's front end.

It is not a bad system "per se", but it goes contrary to my philosophy as far as poppet valve tuning is concerned because I believe that MOST of the closing force for the valve has to be provided by (ideally) the flow speed, and if that is not possible, then the pressure remaining in the plenum or tank.
This is a "passive" way to ensure that the valve will self adjust to the natural lowering of the pressure as shots are taken.
But, that is JMHO. YMMV.

The other difference is the location of the additional ORing.

If you look at the vented version, you will see that it has an additional ORing at the rear, where the regulator's body meets the plenum chamber.

Well, that ORing makes it possible to remove the tank's closure ORing and create a vented reg. BUT, this works MUCH better in the older tanks that had a great finish and therefore needed little inteference for the ORing to seal at the rear. In the newer tanks, a bigger ORing is needed and this creates an unsafe situtation where you MAY think the tank is empty, but there is still pressure in the plenum. SO, BE CAREFUL!

ALTAROS regulators have a great site and their installation has been well documented, so we will not go there.
Suffice to say that ALTAROS regulators are graduated and offer a much better option when you want to tune an airgun to some specific specs and not just "dialing it to 11".

Now that the machining part was done, the "fun" could begin. And I am putting " " on fun because it is a necessary evil to test long strings when tuning a PCP. Otherwise, you are just making assumptions about how the regulated gun is going to behave. Professionals do not do that. Simple.

With the two tanks in hand, a probe and a compressor, we started the tuning process itself, which will not be without its thrills and surprises, LOL!

The tuning process

Regulators were (at least that is what the purchase specs said) set at the factory to 120 BAR's
Now, that is, in truth, a VERY HIGH setting. If the gun needs 120 BAR's to yield decent MV's with a mid-heavy 0.22" pellet, then there is something wrong with the system's design.
It is not a bad setting if you are planning on slugs (which we tested), or pellets in the heavy for caliber region, but for mid-weight pellets it is a wasteful setting.

Anyway, that is what the factory sets them at, and there is no scale in the OEM regulators. On top: there is only ONE manometer in the gun, so that you cannot "monitor" the regulated cavity's pressure.
Your only method of determining what is the Reg'ed pressure is to shoot a whole string and note where the MV drops like a rock.
Following that method will also yield good information about the internals of the system and whether they are "balanced" or not.

Seven years ago, when we were studying the upgrade packages of the Stormrider, this was one of my main priorities; now it is almost a given in MANY PCP's, back then it was revolutionary.
So, with assembled and aired up tanks, we started the testing.
We had PREVIOUSLY, performed a few "benchmark" tests, which yielded VERY poor performances.
This is the OEM non-regulated setting:

The first indication that something is not right comes from the fact that the MV drops DOWN continuously from the first shot.
Yes, there is a lot of power in those 18 shots that are "really good" , but then, most pellets will not stabilize well from most barrels at this MV, so ¿Why use it? ¿Marketing, probably?
Whatever the reason, this was the source of dis-satisfaction about the rifle that my friend and his son had.
Quite understandable.
So, I thought, maybe they drew the spec for heavy pellets and slugs?
Well, here is the result of testing:

Not exactly stellar performance, and those two consecutive low shots with the JSB H's (10.3 grs) showed that there was something fishy going on in there.
The K-O slugs (same weight) performed well and more consistently, so there COULD be an argument made that the idea was to use slugs, but then, something does not "jive" in the balance of the system because the system is rated at 200 BAR's and, theoretically, at least, there are shots that could be taken at higher pressure and use the valve-lock to control the energy output.
So, what went funky in the design and prototyping? the spec of the tank's max pressure?, or the springs in the valving?
Because in principle I wasn't going to spend too much time in this project, I thought, well, we reduce the reg pressure and we'll be fine.
Customer had expressed the desire of 60 shots at 600 fps to make this a "plinker", so there were no real high stakes and just a lower reg pressure should do it ¿right?
Hmmmm, not so. This is the string of a regulated string with the vented modified reg:

Still too high an MV, way beyond useful, though consistency was good.
So we reduced the pressure in the reg to ABOUT 90 BAR's:

At first I tought I had done something wrong, probably "broken" the reg by setting it too low, nowhere could I find any spec telling me what was the min pressure of the reg.
So I tested with the Altaros at 100 BAR

WHAAAT????
We're getting less shots from a lower pressure regulated cavity?
As Hamlet would say: "Something is rotten in Denmark".
But this told us that the problem lied in the action itself.
The action was being wasteful, and there was no further adjustment possible to the valving.

But before that, we need to discuss the hammer adjustment procedure.
And, on purpose, I am not going to show any pictures.
All the videos and literature out there said that, to adjust the hammer strike you needed to put a long 4 mm's hex wrench through the rear hole and screw IN for less energy, OUT for more.
SOME videos told the user to cock the hammer, or to at least bring it back to where the screw was accessible to the wrench.
Well, at least in THIS version, that is total hogwash.
Even under hammer spring pressure the very long grub screw at the bottom of the hammer will make the hammer spin and not "take" any adjustment.
HOWEVER, looking at the bottom of the action, there is a nice little hole a little bit to the rear of the middle stock screw, and through that hole, when the hammer is partially retracted, you can LOCK the hammer rotation by inserting a punch through a corresponding hole in the hammer itself and effect some real adjustments to the power screw.
And so, we tried to reduce the energy of the hammer strike, only to find that it was at its LOWEST.

The grub screw at the bottom of the spring cavity in the hammer dictates the preload of the hammer spring, if it is out, there will be more pre-load, if it is in, there will be less pre-load.
At its lowest setting, the grub screw still protrudes almost 10 mm's into the hammer spring cavity, so this was dictating a LOT of pre-load.

As hard as it seemed, we had to get INTO the action.

The action seems to have been designed by a shotgun gunsmith.
The components are not actually "unitized" and springs are held by the pins that keep the trigger in the action.
Take out the pins to remove the trigger and there are springs that are now axle-less and can be displaced to places where they do not do their job anymore.
AND there is no documentation of how the trigger works.
So let's look at it briefly.
The trigger parts are not that different from all the airgun trigger parts we've seen that seem to stem from the Chinese Crossbow triggers of the 3rd Century BCE.

When the trigger adjustment screws push the lower lever, the front of this moves up and the rear drops down, thereby enabling the rear lever to rotate to the left, allowing the sear's rear to move up and the front down, thereby releasing the hammer from its cocked position.
It IS a good trigger, crisp and clean.
It is also an interference trigger, as opposed to hook triggers, interference triggers are faster.
Why give the trigger blade a counterweight? I assume it is mostly a place to put the first stage spring, though the weight does give the blade a little return force, it is not the determinant force.
Now, springs coming out of their place when disassembling something is not an unknown aspect of airgunsmithing, and the same solution that applies to spring-piston airguns applies here:
Dumb pins.
A dumb pin is a shortened pin that holds the parts of subassemblies in place while the assembly of the whole gun is being completed.
Once all the sub-assemblies are in place, the final pins drive the dumb pins out, the gun is secured and can be mounted in the stock and shipped.

So we turned two dumb pins, 3 mm's OD, 10 mm's long and they worked well.

One dumb pin is installed, the other is out for illustration purposes. With this sub-assembly in place, the action can be dis-assembled and re-assembled again as needed.

For our purposes then the action had to be dis-assembled, the grub screw adjusted to it MINIMUM, and then the whole thing had to go into testing again.

And this is exactly what happened, the grub screw was cut IN HALF, and the gun re-assembled for testing.
Once the power adjustment screw was cut in half these are the results using the Altaros regulator at 100 BAR's in the old tank:

NOW, we're cooking!
57 shots at top speed for mid-weight pellets is a good performance, sample standard deviation of 3.2 fps tells us that 95% of the shots will be between 911.8 and 902.2 which is perfectly acceptable.
If the user can find a pellet that is really accurate out of this barrel, he could shoot most FT matches without worried of refilling during the match. Make sure you start with a full tank, take two shots just before startin the match, and just keep on shooting!
For a light gun, this is perfectly acceptable performance, and, at more than DOUBLE the OEM performance, it was a good point to stop this avenue of development.

Now, the user wanted a "plinker", something in the 600 fps region.
There are MANY reasons why users may want lower power.
Noise
Neighbors
Backstops
Targets
etc.
So we decided to dedicate the Hatsan H tank and the non-vented regulator to reach that goal.
We tried setting the reg at "about" 70 BAR, and upon testing a whole string we observed something VERY interesting:
When the tank's pressure was at about 60 BAR's the valve self regulated!
This was a Eureka moment and we proceeded to adjust even further the OEM H regulator and perform a test.
Because we did know what happened at higher pressures, we started at 150 BAR's:

So, 78 really good shots using 2/3'rds of the tanks capacity, with an ES of about 19, and a sample standard deviation of 6½ fps.
NOT BAD.
DO note that even starting at a lower than Max rated pressure, the first two shots are "penalized" by the non-venting regulator.
Since the express purpose of this tank is to be a plinker, I considered the project had achieved its goals.
As a plinker and using the full capacity of the tank, this combination will yield about 150 perfectly usable shots.
Which means 1 shot per BAR.

Epilogue

As I said to my friend: Now you have TWO rifles.

It's a question of finding a pellet that works for each power level and having two scopes.

If you want to plink, you use the plinking tank and the corresponding scope and get a ton of shots without refilling. IF you want to pump by hand, then do not worry about going much higher than 170 BAR's and you will still get more than 100 shots.

If you want to get more serious, get the appropriate pellets and scope and you still get almost 60 shots per fill at 15 ft-lbs. Plenty of power for the caliber.

Overall, I would say it was successful project.

Hope you have enjoyed the read, keep well and shoot straight!

HM

2 Comments

The DIANA 34 EMS (Easy Modular System).- Chap. 2

1/3/2025

4 Comments

3 ½ years in the making. LOL!

Yes, just like the "Three Musketeers" had a sequel that came well after the initial book, the original "Chapter 1" took some years to "coalesce".

Now, with some talk about returning to the "Classic DIANA 34" it is essential that we truly get into the differences and rescue what is worthwhile from the EMS.

Just to remind everyone, the EMS took the NTec piston and trigger unit and came out as a steel spring powered version.

We have already explored the conversion of "Old 34's" into NTec systems (and in Chap 1 we detailed how to install an NTec unit into an EMS rifle), so, we won't go there. Rather, we'll use the first part of this entry to explore the intrinsic advantages of the EMS system as well as some of its "caveats" and, in a second part, relate in detail what makes the steel spring version of the NTec triggered airgun such a success and how to go about it.

As usual, the disclaimer is that all the operations performed here were done by a qualified airgunsmith who took all the precautions of the case. No warranties are implied or extended, and no responsibilities will be accepted.
If you decide to do this, you are on your own.

SO, let's get into the first part.

What makes the EMS a better airgun?

In this, as in most things in life, there is a lot more to an object than "black and white"; or even "Umpteen shades of grey". Life is colorful and we all have our likes and dislikes. So, to be clear: All the following aspects are my opinion, based on more than 24 years of airgunsmithing, out of which, 12 have been at a professional level.

We'll only make two comments about the stock:
- Apart from the ghastly buttplate that is used in the EMS "Classic" that slips on every smooth surface known to man (floor, shirt, or jacket), the stock is quite traditional and svelte, light and nimble to mount to shoulder.
It also has the cutouts to allow the regulation of the fork's tension across the barrelblock axle:

Anyone that shoots/hunts in diverse temperatures (from the 40°C of summer to the -2°C of Winter, knows that this sometimes needs some "adjustment" to the specific conditions.
Underneath the screw and the "nut" there are loc-washers that make the system very reliable.
So, this, I would keep.

In the attachment of the stock to the mechanisms tube, the EMS uses angled screws:

This is a far superior method than the bracket that was used in the "old 34", yes it requires a slightly "beefier" stock in this area, but it it less prone to catastrophic failure.
The Caveat here is that a cross threaded, or broken screw, means serious business and is not as easy to resolve as the changing of the bracket itself. So, yes it is a superior system, that requires superior caution and care when working on one of these guns.

The cocking linkage is next: the EMS uses a compound cocking linkage:

This allows the slot in the stock to be far shorter than the slot in the "old 34" stock, it also reduces the peak cocking force.
For the gunsmith, however, the main advantage is that you can flip the mid-junction up, as in the photo, and with the barrelblock in the broken open position, the linkage comes out and you can withdraw the piston for any work needed without disassembling the cocking linkage from the barrelblock itself.
This saves a ton of time when you only need to change the piston seal.
The Caveat here is that the stock then becomes an integral part of the mechanism of the gun, as it is the stock what maintains the cocking lever in the right position throughout the cocking cycle.
To ME, that is not a disadvantage at all, but some may not like it.

Now, IF, for any reason, the cocking linkage needs to be worked on, it is a very useful characteristic that the "axle" of the cocking lever is not affixed to the barrel block by a simple pin with an "EClip" lock, as in the "old 34", or using a pinned in pin, that needs to be driven out with a hammer and a punch, as in other brands.
In the EMS, the cocking linkage pin is a shoulder screw with a torx head:

And this is locked in place through a cross-grub screw on the other side:

Is this "over-engineering"?
I don't think so. It makes the gun serviceable in ways that only create problems otherwise.
Perhaps it is a matter of customer education. I've seen more rifles damaged by people that want to hammer out the corresponding pin from the wrong side, than I can tell, and the problem is that customer comes to the gunsmith with the complaint: "I didn't do anything wrong, just punched the pin out, and now it does not want stay in". LOL!
Anyway, this is another of the things I would keep.

Keeping to the barrelblock: the barrelblock was designed with enough space to insert a locking mechanism.
There has not been a strong market reaction to this possibility, so it may never happen, but since the locking mechanism's patents have expired a long time ago, perhaps it is time to use the existing state of the art. We'll see what happens on that one.

The next one is one where I am ambivalent: on one side I dislike it, on the other, not so much and even think it is an advantage; I'm talking about the scope rail:

The scope rail is CNC cut into both sides using a dovetail cutter, that enters, cuts, and then comes out.
It is elegant and clean, excellently executed:

The other side is the same.

IF you are using a fairly common mount with sideplates that make the dovetail when closed by the tension screws, you're OK. But if you want to use one of the best bases (BKL's), then you run into problems.
Of course, if you use a ZR mount, you're good on all counts, it is high enough to give you clearance for even large objective lenses (not that the 34 has need or use of FT type scopes, but the facility is there), and you can also open the sideplates enough to properly insert and clamp the base.

IF you want to use a Peep, then it is a bit more complicated. Williams' do fit well, but the more elaborate Match/peep sights have real issues getting into these slots. Do many people install a $200 peep sight in a $400 rifle? not so many, but it is something to consider.
One possibility is to continue the dovetails all the way to the rear, so that, removing the dust protector at the rear, you can slide in anything that has an appropriate dovetail mounting system.
The other possibility would be to re-instate the DIANA scope rail, but, IMHO, that would raise the LOS too much and would add weight and is a potential failure point. I've seen less than half a dozen failed rails in all my life; and most of them have been user-induced problems, but still we need to be candid about both sides of the issue.

Now, let's get to the internals:

Last, but not least is something that bothers me as a gunsmith, it seems to me to be a "shortcut" something that should not happen because, "really, we know better", and that is the angle of the transfer port.
In the EMS, the transfer port is coaxial to the bore, and is located at the top of the compression chamber which means that it is offset from the compression chamber.
What this means is that we do not have an efficient transfer geometry. Yes it is shorter, it is the shortest distance between compression and expansion possible, but it forgets that the piston seal is on the way:

Here's a piston seal that has seen a few dry-fires and/or has been oversprung and so the second hit of the piston against the compression chamber end wall is really strong.
It not only opens the seal to damage, but it also interferes with the flow of very hot air at very high pressures into the transfer port.
There's a famous "birds foot" piston seal from another manufacturer, that has not worked too well either.
Yes, the TP needs to be kept as short as possible, and it does benefit from a certain degree of venturization (in break barrels), but this should not be executed at the cost of disrupting the end of a compression cycle that is almost a detonation.

The NTec trigger was designed from the ground up to be a piston body/locking trigger, to alllow DIANA to dispense with the stem and insert the gas spring, that, by itself, is a stemmed device. In order to "lock" everything into a unit, DIANA made a special "cup" that holds the piston in place when fully cocked, this cup then receives the body of the gas spring while the stem of the pusher element goes into the piston.
The trigger therefore, needed a nut. So as to screw the body of the gas spring into the trigger block:

At the top, you can see the safety carrier plate that also acts as a cocking lever, and in the center you can see the threaded part that acts like a "nut" retaining the gas spring body.
At the bottom is the actual "sear" that is a ramp that interferes by pushing itself into a square hole in the bottom of the piston.
When the lower lever pushes the upper lever and the sear "breaks" what is happening in reality is that this little ramp "falls" and allows the piston to fly forward.
Now, to make it possible for this mechanism to work reliably, the POSITION of the piston has to register to within 0.010" each time the piston is cocked, and without the support and alignment of the stem and guide, a "cup" needs to be added, like this:

In the case of the NTec rifles, the male thread is part of the gas spring, but in a steel spring gun?

We use a very special screw:

Now, in true DIANA tradition, this is an ISO/DIN part. It is a standardized screw. Not common, but it is a standardized screw.
In the US it is obtainable from the better industrial supply houses.

Conversion of an NTec airgun to a steel spring one

So, now that we understand how critical it is to have the piston in exactly the same position every time, we can understand how the EMS uses a steel spring powerplant:

So, there are FIVE parts in this picture of the powerplant, from left to right:
-Screw (almost invisible, you only see part of the thread)
-Cup
-Spring guide
-Spring
-Forward guide
Wait . . . ¿WHAT? a forward guide?

Yup!

It is a forward guide and also a piston weight.

Without this forward guide, there would be a LOT of spring breakages and the power achievable would be cut significantly, especially for mid to heavy pellets.
We need to remember that the 34 and all its variations: EMS, AM03, 340, are break barrel, and that means a long transfer port. Weight in the piston is essential to ensure proper energy transfer through the transfer port.

I have tested different arrangements of forward and rear guide, some of them worked in some guns, some made funny noises during the cocking stroke, some of them worked in some but not all guns, some of them worked with one spring but not another, some of them worked for a while, but did not have the long term reliability that DIANA demands from their products. So, after DOZENS of tests and hundreds of shots, CCA has decided to stay (for the moment) within the OEM design, just use much tighter tolerances:

At the top is the OEM components, at the bottom is the CCA rear spring guide and front piston guide.
The differences of a some thousandths in each dimension (internal and external) are not visible in the picture, but the quality of the shot cycle is night and day.

So, what can we expect from converting an NTec rifle into a steel spring powered rifle?
Taking advantage of a request from Eastern Europe and with infinite thanks to my Serbian friend for his patience and forbearance, I performed a full/organized test of all the methods I had used in the past to get to some conclusions.
Please bear in mind that nearly a thousand shots were made to reach these conclusions, they are not the result of a few groups/strings.
Using a well characterized pellet (the JSB Exact 8.44/4.52) in a recent production EMS in 0.177" cal. and using the Titan XS spring #3, the results are as follows:

With the NTec unit the rifle yielded on average 13.8 ft-lbs (860 ± 3 fps) as measured by a Caldwell chrono with IR screens at a controlled distance.
With the CCA components and a full size Titan #3, the gun yielded 14.6 ft-lbs (883 ± 2 fps)
Since my friend is going to use this rifle as a practice rifle for UK/HFT, the rifle needed to yield sub-12 ft-lbs.
We had to cut 3½ coils off the spring to achieve this.
Now with the shortened spring, the gun yields 12 ft-lbs (798 ± 2 fps) and with heavy pellets, like the H&N BFT, it yields 11.3 ft-lbs (731 ± 4 fps).

The Titan #3 can be spaced up almost 0.040" / 10 mm's, but while the speeds do go up, the shot cycle becomes less than stellar.
If more power is wished, accepting the cost of a harsher shot cycle, then it would be advisable to use the Titan #4.

I don't have a 340 Ntec, to test, nor a 350 NTec. And, quite frankly, this whole thing has taken far too much time, not a bad investment, but there are other things that also need to be addressed, so this will be the end, for the moment of this development. IF/ WHEN there is a solid interest, we may retake the idea again.

The fact that a properly built steel spring powerplant is superior, not only in power, to a gas spring; but also offers a much better shot cycle for a given power is interesting.

The LIMITS of the above statement is when using heavy for caliber pellets; in that situation, the gas spring does become a better powerplant, limited only by the swept volume, the barrel length, and the transfer port geometry.

For example: my D34 converted into NTec in 0.20" cal and a short barrel, develops 15.2 ft-lbs with JSB's 13.4 (715 ± 3 fps) , and 16.7 ft-lbs with H&N FTT's (811 ± 3 fps) , while in 0.177" cal, even using a longer barrel, it only developed 13.8 ft-lbs
I need to get some heavy 0.20" s from JSB and test, but that will be another story.

Keep well and shoot straight!

HM

4 Comments

The Mauser K98 S (Spring) by M&G

12/18/2024

4 Comments

A true Mauser

The Mauser K98 is an iconic weapon, a lot has been written about it and we'll not go there here.
What is important is that Mayer & Grammelspacher (makers of DIANA airguns) now belongs to the same industrial group that owns Mauser (among other prestigious brands), so M&G/DIANA can, in all honesty, make and market an airgun under the Mauser brand.

The first time this happened was with the launch of the AM-03, an airgun version of a current Mauser sporting rifle.
We have already reviewed and commented on that one, so we will also skip that.

The second time it happened was when M&G decided to make a "facsimile" of the venerable K98 using the D460 Magnum as a platform/chassis.
The 460, being a svelte and powerful lady made a lot of sense as a spring-piston version of the war horse that is the K98.
There is another version still, as a PCP, but we will tackle that at a later date, as it has much in common with the Stormrider and we have explored that one fairly in depth.

So, what we are looking at in detail today is this:

Nice! ¿No?

Well, a few "pundits" have complained that (insert Gilbert Godffrey's voice here:) "it lacks a bolt".

Ok, so, this is the difference between a replica and a facsimile.

Replicas are supposed to be identical to the object they replicate (am I making sense here?) .

The word "facsimile" comes from the Latin "facia" and "similes", which means "similar face".
In a DOCUMENT, a facsimile is an identical copy because a document is nothing but a "face", in more bodily goods, a facsimile is understood as being "similar enough" , but not necessarily identical all around.

So, having clarified that, perhaps we also need to say that the idea had been brewing for a number of years.
Back in 2018, at the IWA, DIANA showed this:

That year, we had good, long, conversations with my friends Michael Swoboda and Florian Hassler, CEO's of M&G who are great fans of history and finely made guns so, this model holds a special place.
In here, I have to say that Florian will be retiring from DIANA/M&G at this year's end and that, personally, I will miss him much. We may have not always agreed on technical stuff, but the respect and gentlemanly conduct of the person made him very dear to me.
Back to the k98: the model was produced for a few years and, due to economic conditions, is now out of the catalog; at least for the foreseeable future, but there are enough around that they merit a study in depth.

A project is born

Back in November of 2020 (yes, that is a long time ago), a friend asked me a BUNCH of questions about the K98 S (for spring), and they were dutifully answered. Little did I know that it would "unchain" a series of events that would take years to consolidate into a solid idea.
First of all, my knowledge about the different models and issues of the k98 was somewhat sparse.
AaMoF, even the "experts" could not agree on certain aspects, like which scope, how it was mounted, how did the stripper clips fit into the picture, was the "grunt issue" buttplate always in place, what other modifications were done, etc, etc, etc....

As my enquiries progressed, two notable companies with whom I do some small, but interesting business, started asking ME questions!?!?!?
Wait, what? I am the one that asks the questions here, LOL!

It ended up that they came up with VERY interesting replicas (now these are TRUE replicas) for parts that are extremely scarce, and yet highly sought after. Now the powderburners have access to replicas of parts that might enable them to build a SS K98 using old actions/basic guns available in the surplus market, into something historically accurate and functional.
BTW, there are matches that are limited to originals or true replicas, and very few will enlist a $24k gun into a match, LOL!

We'll come to that in a moment.

The other thing that happened, was CoViD. Yes, the world stopped for almost two years. And it took one more year to get all the delayed stuff over!

Once everything was sort of back on track, we could take up the project again.

In here, I have to extend to my friend/customer my heartfelt gratitude for his patience and understanding.

So, where does one start?

"In the beginning"

Famous words from one of the most read books. But, back to airguns:

In the beginning there was an idea:
To turn the k98 S into a shootable/enjoyable/accurate/easy to shoot machine; while respecting the "spirit" of the beast and its specific incarnation as a Sniper's Tool (ScharfSchutzen Gewehr-SSG)

Most of us are fairly conversant with the two main "embodiments" of these:

The small, forward mounted scope:

And the quick detachable "high mount" that offered the opportunity to use the iron sights on the fly:

When developing these ideas, there is no alternative but to get, physically, the parts you need, or believe you will need and "try them on for size".

So, in this way I came about getting this:

Yup! My good friends at Vector Optics made a run of replica mounts for the 98k. And I mean replica.
They allow the use of the iron sights:

The mounts are "claw" style in the sense that there are "tabs" that secure the front mount:

Then the whole assembly gets inserted:

And rotated:

So that the "claw" at the rear slides in and catches

And the mount gets locked by turning the rear lever to the back:

There is absolutely no doubt about the strength of this arrangement, and it incorporates windage adjustments:

The scopes themselves had the elevation turrets.

As much as I like this system, we could not use it and still keep the "scope forward" mounting version.
MOSTLY because the D460 is loaded exactly at the point where the original forward mounted scope would be.
There is nothing as displeasing as an airgun that is hard to load.

The last thing to mention that is interesting for us, airgunners, is that the mounts allow for "droop mount" compensation:

If you are wondering why mount the parts into wooden "dummies", it is because these parts are made to VERY TIGHT tolerances, and so, you need to "work them well" BEFORE installing.
You do NOT want your scope to be the lever that "loosens up" the mounts.
The curvature of the mounts follows VERY closely the curvature of the mechanisms tube in the D460, so soldering the mounts would have presented no serious trouble.

I MAY use these mounts in another specimen that will be upcoming. But, for THIS specific version, where the user wanted a "forward mounted" scope, we ended up having to use a "reversed" version of the Hawke adjustable dovetail to weaver rail with extension.

The OEM part starts like this:

But it is designed so that the extension protrudes to the REAR, if you see in the picture above the "hinge" is located on the opposite side to the extended part of the rail.
So, the reversal starts with changing the arrangement, and because we wanted no "slop" we started by turning a brass pin to replace the loose hinge pin in the OEM piece:

We had to relocate the droop adjustment screw and the locking screw:

And then the rail could work as we wanted:

Do note that the k-98 S's loading port is "clear" of the scope's bell and loading is not a problem.

Not bad, ¿huh?

The other part that came from a totally unexpected source was the "Geriffelt Schaftkappe". One of my main peeves about the K98 S's (and I've sold a few) is that, for precision shooting, the smooth buttplate simply does not "cut it". It slips at the worst possible moment.
I always wondered how the snipers of the time adjusted to that, and I found pictures of a number of rifles wrapped in rags, others with filed marks, and still others that had actually received a "grooved" (geriffelt) buttplate (Schaftkappe).

So, when I received this from my friends at ADE:

I was very pleasantly surprised.

The difference is day/night:

Now, you MAY think that the replacement isn't a direct one because the stock screws do not align, but the reality is that the stock-maker actually replicated the stock's rear, and the stock DOES have a screw hole in the right place.
These butt-plates are VERY strong pieces (after all, the butt was part of a war implement) that are like a "cuff", meaning that they go OVER a "reduced" section of the stock. I was somewhat fearful that the reduction would be different in the Mauser by DIANA stock vs. the original Mauser version, but lo and behold! Perfect fit!

With the addition of a leather cheekpiece, combined with the very low rings and small scope, the rifle can be used with both, iron and scope sights.
The leather cheekpiece can be available in RH or LH version and you can cut slots in the "off side" to allow the two part Mauser K98 sling to be used.

The rail and the scope rings do not allow the simultaneous use of the iron sights and the scope, but by removing the scope WITH the rings, the iron sights are clearly usable:

A quick walk-through of the ergonomics showed that we had achieved the objectives:

Looking through the scope was an interesting experience, at 2X it offers a wide field of view:

At 7X it affords quite a lot of detail:

So, now that we had the "dress" it was important to get a performance that honored the likeness.

The Powerplant

The idea was to have a 13 ft-lbs springer that could be shot all day without too much fatigue.
So, initially, I had thought about using a short stroke piston:

AND the output was there. BUT the cocking stroke could not be altered in such a way as to reduce the PCF (Peak Cocking Force).
Exerting 45 # F, even for a short arc still requires the human to exert the force, and humans fatigue on the force exerted, not the total energy input.
So, building on the work previously done in the LGU Ultra Light (UL) Piston, we devised one for the D460.

We used a Titan #1 spring, with one coil lopped off.
In here an important note:
The "NEW" Titan #1 is not the one we had come to love. And I cannot but blame our European "cousins" that complained endlessly about the #1 not being a "standard power" spring and being "too powerful and not a drop-in for 12 ft-lbs". The "NEW" #1 is a good 0.010" larger in OD, and 0.002" smaller in Wire Diameter.
And those differences are important, just plug the numbers in a spring rate calculator.
The other aspect is that the ends of the spring are not forged parallel.
The ends are somewhat "conical". The last coil or coil and a half are substantially smaller than the ID of the rest of the spring (0.583" vs. 0.624"), so that created a huge headache. We ended up "opening up" the ends.

And had to turn two different guides.

Anyway, by using an UL piston, we could "tune" the shot cycle to the power we wanted and the pellet the barrel preferred by modifying the weight of the top-hat alone, while keeping the PCF to 31 # F.

Extensive tests in a D52 platform yielded interesting results and by the time we settled on an arrangement, the whole was transplanted into the k98 S.
Results were a bit on the low side to start with:
JSB Xact .- 11.6 ft-lbs
H&N B-8.- 12 ft-lbs
QYS SL.- 12.1 ft-lbs

So we changed the top hat to a heavier one:
JSB Xact.- 12.9 ft-lbs
QYS SL.- 13.2 ft-lbs
H&N B-8.- 13.2 ft-lbs

BINGO!

The lowest spread was obtained with QYS SL's, but those pellets are not easy to obtain, so we did the rest of the tuning with the H&N B-8's

In the end, after about 500 shots the gun was yielding 838 ± 4 fps with the H&N B-8 that are 8.44 grs. (nominal).

The process

We'll be tacking here the K98 S serial # 25030667, which should be fairly typical of all others.
To disassemble a Mauser K98 S you will need some special tools.
DIANA includes them in the box, so if you got your gun second hand, you may not get them.
One tool is for adjusting the front sight's elevation; the other, the most important one is a 3 mm's thick 16 mm's wrench.
You can make one from a bicycle wrench in 5/8" if it does not happen that the tolerances in these cheap tools allow dual usage.

The notches are to allow the use of this tool also for tightening/loosening the scope rings.

You need to remove the muzzle piece:

There is a tiny retaining screw at the top, behind the sight blade that needs loosening. Do NOT forget this!

The tiny screw at the FRONT of the front sight base is to set the blade. The blade gives you a wide range of vertical positions by screwing in and out the whole blade.

Do note there is a flat at the bottom and the piece will always align properly. Just do not force it.

Once that is done, then the "train" can start coming out. Open the lever:

And using a shaped block, tap to remove the front metal guard:

This will allow you to slide out the first "wagon":

Now, keep that part as an assembly:

And note that there are small pins and big pins. You CANNOT assemble the part in the wrong orientation if you follow those. Now remove the second metal part and put it in the train:

You will now need to disassemble the stock from the action because there is one piece that is "keyed".

Loosen the fore end screws and the rear stock screw (front trigger guard screw):

Check the screw wells for damage by the star washers:

Clean it up

You will need to reinforce that with some steel flat washers. That will be done later.
Remove the rear stock screw and now take the action out of the stock:

Now you can slide the top wooden piece out of the barrel:

If you look at that part from the front, you will see how it is "keyed":

And now you can put together the whole "train".
Keep it all together in a box, old scope boxes work very well for this:

Now you have a D460 action you can work on:

On of my favourite parts:

"Look Ma!, it's a genuine Mauser"!

Put the action in the compressor, replace the action pins with the dumb pins, open the action and remove the power plant:

The cocking lever arrangement is disconnected:

And the lever linkage is disconnected from the compression chamber:

Once the compression chamber is extracted, the breech seal can come out:

To my surprise, a spacing washer came out.
We had to turn a special reinforcing insert and replace the seal with a new one:

The barrel was cleaned:

And the inside of the mechanisms tube was de-burred / polished:

Now the barrel work can start.
As it has become somewhat "normal" for DIANA airguns in 0.177" cal., the barrel's leade was too lose for the precision pellets we normally shoot (JSB, H&N, QYS), so that leade needs to be shortened.
Because the 460 has an offset barrel in relation to the compression chamber, we needed to make a special tool:

The brass pilot was turned to the diameter of the chamber (that differs from the diameter of the barrel at the choke). The tool also needed to connect to a manual drill and extensions:

To reach deep into the D460 action:

We made sure everything was square:

And removed about 0.5 mm's:

Once that was done, we performed the trigger work and affixed the external retaining rings we use in all our builds:

The powerplant was changed and upon assembly, we took care of the screw wells by gluing flat washers at the bottom:

And replacing the star washers with Nord-Loc washers:

The assembly went in reverse order EXCEPT for the addition of barrel shims between the barrel and the barrel sleeves.
This is a part hat DIANA uses in ALL the rifles under the 48 -> 56 model numbers, so I do not know why they excluded it in this model that, because it has so many "thingies" hanging out there, needs it the most.
Shims were cut from larger stock and sized precisely to the lengths needed:

To cut thin materials, you need to use a mandrel:

Now we have a superb fit:

ORings added:

And a magnet glued to the spot where the lever needs to be held.
If the gun is disassembled, then upon assembly, care needs to be taken to align this magnet with the cocking lever to make this secure.

The results

Now, was all this work worth it?

I would answer with a resounding yes.

I took advantage of an outing to the WAC-DIFTA airgun range to test it at distance.
And, on, purpose, did not take any other rifle apart from this one.

For starters, it is truly a beautiful lady, and once I became somewhat familiar with the 7x scope and the duplex reticle (a FAR cry from the 30X Xmas tree style I normally use), this Valkyrie (war lady) allowed for a more than reasonable performance.
Targets were set at 10, 25, 40 and 55 yards; on one hand to reflect the distances that the Pyramyd Air Cup "Gunslynger" silhouette style shoot is shot at, and on another, the max distances allowed in WFTF for targets of 15, 25 and 40 mm's diameter.

The FT targets were for my friend Toby, that is starting his FT career

I am still hopeful I can convert him into a Spring-piston shooter, LOL!
The silhouettes were mainly for the K98.
The first round of 20 shots, was taken to decide HOW to sight in the rifle:
The chicken:

The Javelina (wind started picking up):

The Turkey (I started paying attention to the wind):

And the Ram.
I had no idea where the shots were going to land, but the fact that all the shots are in a horizontal line told me the pellets were being stable at this distance, and that was a huge success:

After retrieving the targets and taking some measurements, I decided to sight-in the rifle with the crosshairs, dead on at 25 yards and holding off for range and wind.
These are the results, do note it is a 7x scope, LOL!

The chicken:

5 hits, now the javelina:

Another 5 hits and still refining the POA's, now the turkey:

At this distance, the hits are no longer visible through the scope still, not bad, 3 hits on the hardest target in the silhouette game from a 7X scope. Not too shabby, at all.
Now the ram:

Aaaarrghhh! The wind got me.
The ram was located above all the other targets, so more open to the wind.
Still, not bad.

Would I be competitive in a current Gusnlynger?
Nope! LOL!

It is a young man's game now. I shot 20 "for score" shots in 2:45 with 3 misses

The current youngsters shoot all 20 targets down in 1:30

:-( LOL!

Still, it was a wonderful experience shooting the K98 S SSG at extended distances.

It COULD be a good gun for Hunter-Piston under AAFTA rules, perhaps shooting a bit "hotter", something that this platform is perfectly capable of doing. The 55 yards "group" printed on the Ram measures 30 mm's c-c, or 35 mm's O-O, so they would all have gone into the 40 mm's kill zone, given correct wind reading, a better scope (up to 16X allowed under the rules) and, most importantly, a better shooter, ROFL!

There are several factors for the accuracy and precision of the K98 S SSG in this tune:
1.- It is a heavy rifle; 10 # with a small scope
2.- Barrel is tensioned
3.- The shot cycle is extremely fast, it is not even a "thump", it is more like a dry "TK"
4.- The rifle proved to be hold insensitive.

There are still some of these rifles around that are available, if you are in the market for an interesting piece of history that is, at the same time enjoyable and useful (could be a great hunter in 0.22"), then look into it.

Thanks for reading!

Keep well and shoot straight!

HM

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Hector Medina

2012 US National WFTF Spring Piston Champion
2012 WFTF Spring Piston Grand Prix Winner
2013 World's WFTF Spring Piston 7th place
2014 Texas State WFTF Piston Champion
2014 World's WFTF Spring Piston 5th place.
2015 Maine State Champion WFTF Piston
2015 Massachusetts State Champion WFTF Piston
2015 New York State Champion WFTF Piston
2015 US National WFTF Piston 2nd Place
2016 Canadian WFTF Piston Champion
2016 Pyramyd Air Cup WFTF Piston 1st Place
2017 US Nationals Open Piston 3rd Place
2018 WFTC's Member of Team USA Champion Springers
2018 WFTC's 4th place Veteran Springer
2020 Puerto Rico GP Piston First Place
2020 NC State Championships 1st Place Piston
2022 Maryland State Champion WFTF
2022 WFTC's Italy Member of TEAM USA 2nd place Springers
2022 WFTC's Italy
2nd Place Veteran Springers
2023 WFTC's South Africa Member TEAM USA 1st place Springers
2023 WFTC's South Africa
2nd Place Veteran Springers

Hector's Airgun Blog

Exploring the Steel-Spring'ed EMS powerplant

Using a 34k in 0.20" cal

Playing a little with a DIANA 58

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The Hämmerli Pneuma

What is, exactly a "Hämmerli Pneuma"?

The Project

The tuning process

Epilogue

The DIANA 34 EMS (Easy Modular System).- Chap. 2

What makes the EMS a better airgun?

Conversion of an NTec airgun to a steel spring one

The Mauser K98 S (Spring) by M&G

A true Mauser

A project is born

"In the beginning"

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