Most of you know me as just another spring-piston guy dedicated to Field Target.

But that became pretty much the single track ONLY after I moved to a reasonable altitude.
​
For most of my early airgunning history I lived near Mexico City (8,000 FASL), and hunted in the surrounding mountains (10,000 FASL). A spring-piston guy I WANTED to be, but couldn't.

So, between 2001 and 2010, I developed several interesting PCP's; from hunting Steyr's (bases for the later "HP" models), to highly sophisticated Talon SS's.
One platform provides the exquisite precision of Austrian gunmaking, the other provides a superbly simple device with huge potential under a proper understanding of the in-line valve so seldom encountered in commercial airguns.
It also helped that I had, and have, personal connections to the CEO's and Inventors of both guns, LOL!

Anyway, the usual disclaimer:

Modifications made to the gun in this blog entry were made by knowledgeable professionals, do NOT attempt to replicate. They proved safe in the specific gun in question.
NO WARRANTIES, expressed or implied are given with this publication, if you modify your gun, you are responsible for the modifications and their consequences.
No "fit for purpose" guarantees are made and the responsibility of proper function remains with the manufacturers and importers of the specific products herein reviewed.

So, with that out of the way, let's get to the System:

In 2002 I got my first Talon, I had a trip to Arkansas, to visit my good friend Tom Anderson (R.I.P.) at the Buzzard's Bluff for the airgun show at Little Rock, and I had it delivered there.
After some time using it in an OEM configuration, I started adding/deleting things; from baffles to a "High-Flow" valve, to the infamous, and completely useless, safety.
When a friend asked for a custom build to yield 50 shots at 35 ft-lbs with a single 20 BAR's fill, was when I discovered the true potential of the in-line valve. And then the Mid-Flow valve came into being.

A valve that was designed to CLOSE ITSELF upon reaching a specific flow rate.

Now ¿Just what is a "Flow Rate"?

Well, the definition we apply here is best exemplified in this diagram:

As you can see from the drawing: Average V (V with a dash on top), is the velocity of the fluid; A is the area of the conduit, d is the distance traveled by the fluid in a certain amount of time t.

In essence, a valve that closes itself upon reaching a defined Flow Rate (Q) means that the valve closes when the speed of the fluid (air in this case) through the conduit reaches a certain point.
And so, if you have the same speed of the air flowing into the barrel behind the pellet, it stands to reason that the velocity of the pellet at the exit of the barrel also has to be the same every time.

In reality, there is nothing perfect, but this simple arrangement is pretty close. There are no moving parts, no regulator, the pressure itself behind the air in the reservoir is the main closing force (the valve uses a very weak "starting" spring for the closure), but the true force of closure comes from the pressure in the tank. More pressure creates a quick closure, less opening time, but because the whole thing is triggered by the flow rate, it is very consistent in the MV. Standard deviation for 10 and 30 shot strings at 850'ish fps was 3 fps.

AND, to improve on things, the Power Wheel in the rifle ACTUALLY becomes a working control.

To give you a few examples:
With a 12" L-W barrel in 0.22" cal, the short rifle yields:
34 ft-lbs with the Power Wheel at 4:3 and Baracuda Match (21.1 grs. pellets)
At 6:3, the gun yields 36 ½ ft-lbs with still a good shot count.
Using JSB Monsters (25.4 grs), with the PW at 4:3 it yields 34½ ft-lbs
At 6:3, it yields 37¼ ft-lbs
At 8:8, it yields 39½ ft-lbs. And then it settles into the strongly diminishing returns section.

I decided to settle on 853 fps average MV, getting 55 perfect shots at ± 3 fps of standard deviation. The gun uses 26.2 cc-BAR / Ft-lb so it's not extremely efficient, but it is not a bad number for the power level.

The forend was taken from an old Benjamin, and the pistol grip was carved by a friend in Argentina. What you see strapped to the front section is the remote control for the laser rangefiding scope. Yes, that "small" scope is a laser rangefinding scope with quite impressive capabilities, but more on that later.

Accuracy wise, the gun seems to perform better with the H&N Baracuda Match, this being a typical test target:

Groups 1-5 are different tests and intents to get a grip on the wind drift. Some groups are 5 shot groups, one group is a 10 shot group, and the important #6 group is a 3 shot group after a 20 minutes rest, dealing with he wind blowing between 3 and 15 mph.
​In the old days, the barrel liked very much the 18 grs Jumbo, but I am out of those for the moment.
​
Not bad at all for a 33" carbine with a 12" barrel that weighs in at 7# 10 oz WITH the laser rangefinding scope and the remote control.

In a hunting airgun, the scope is as important, if not more than the rifle itself, once certain minima for energy, accuracy and precision have been met. This scope was an interesting find at the 2019 IWA show, but it was not until now that I have had the chance to put it through its paces.

Scope is made by Opteck, a company based in Canada, and the scope is a peculiar unit.
Laser rangefinder is specced to provide readings between 10 and 750 meters, which makes it ideal for airgunners. It also is a relatively simple device because it does NOT have neither elevation nor windage adjustments.
In order to keep everything simple and as weather proof as can be (scope is rated IPX6), there are as little external perforations as possible. So, how do you manage?
Answer lies in the smart base. The BASE is adjustable for windage (60 MOA) and elevation (90 MOA).
Now, BOTH adjustment dials are on the sides. AND they follow the Central European method of stating where the impact IS, not where you want the impact to MOVE TO. But, once that is understood, adjustments are just like any other device.

Scope is 10X32, fixed, with controls for reticle focus and for parallax/image focus. Powered by a single CR123 battery, it is not difficult to keep fed.
An auto-shut-off after 15 minutes works like a charm, and the remote control uses a CR2032 battery.

The display is also unique:

Do note that at the top of the viewing window we have:
Distance to the target (the small tree with the white flowers in the picture), angle of the shot (to the right), rifle cant (the two lines appear and disappear as the rifle is canted one way or the other).
Simple, but effective, a lot of information for the long range shooter.

Now, what about the gradation in the reticle? Well, our friends at Opteck put this diagram in IPHY (Inches per Hundred Yards), or "shooters MOA"), but in reality those divisions are metric and are in mrads and halves of mrads:
​

In other words, this:

This scope would be interesting at almost any price.
No other scope can boast of the same rangefiding capabilities.
No other scope can boast of the same IP rating
It combines three ADDITIONAL things that are critical to the long range shooter (and in airguns that is anything beyond 40 yards/36 meters): Slope meter, level, and rangefinder.
Reticle is clear and not too complicated. Personally, I would like a more "informative" reticle, but with the laser rangefinder, that is almost overkill.
Glass is clear and even at 10X, it is not overly dark for a relatively small package.
And it is a lightweight device (under 17 Oz.), when you compare it to the scopes I am used to for FT.

Since I am going to declare war on a band of depredating deer (the little tree with the white flowers is the only one remaining of three that were sown some time ago). I am sure this system will be an important element.

;-)

Keep well and shoot straight!






​HM

Luckily, there is no disclaimer for this one! LOL!

​Let's take a break from harmonics and look in detail at ways to sling airguns.

As a custom gunsmith, I am often requested to put sling swivels and add a sling to the package.

When I ask the customer HOW he would like his rifle slings installed, the answer is always: "As always", or "The only way you can do it".

In reality there are two major ways of installing slings in sporting rifles and within those two ways or locations, you can choose between two hardware styles

The first location and indeed common to the edge of being the only one seen commonly in the USA is what we will term the "American Way". And it is basically en evolution of the military form of slinging the bolt actions: Slings go on the bottom of the stock because rifle is always carried muzzle up

But there are other ways of slinging an airgun, for example, the Europeans like to sling some guns on the side:

Reason is simple: This is a "bergstutzen" (literally: mountain carbine), basically a short, light, carbine design, mainly thought for mountain hunting.
When the rifle is carried up and down 99% of the time, the rifle lies flat against the back and provides a much more comfortable "carry".
A slightly better installation (and more expensive), is the "Pachmayr Flush Mount" swivels, not always easy to obtain:

In this type of installation, the sling needs to go into a special swivel that you need to push and turn for it to lock inside the cavity. Once inside it is perfectly secure and can move back and forth, as swivels should, but you can easily remove the swivels and the surface of the gun is as clean as it can be.

Buying a $100 tool to install one or two slings, is not truly worthwhile for most shooters.

The bronze inserts on the left were made to use the tool to locate more conventional swivel holes.

Of course, you can mix and match, as you see fit:

In this example, the shooter wanted a comfortable way to carry the gun, but still wanted the possibility to use the sling as a "hasty sling" when shooting prone. Something you can easily do with the DIANA 54.

But, ¿what can you do with breakbarrels?, some may ask.

Well, in essence you can choose how to install the rear swivel in any of the two ways: bottom or side, but the front?

This is one way, using a "Magazine Tube" sling, usually employed in Rimfire repeaters to attach the sling swivel to the barrel.
I like to install it as far to the rear as possible, because in that way it interferes the least with the shooting itself.

It does need some care in the installation because there is a hollow screw that attaches the two sides.

I usually install  a thin piece of leather or rubber to protect the finish and also to prevent sliding of the stud along the barrel.

The finished job is quite good and functional because at the rear of the barrel, the pressure or pull on the sling will not open the barrel either.
I always recommend a muzzle down carry with this method, but it is not always possible to do it comfortably if the customer chooses the bottom installation of the rear swivel.

The other option for break barrels is to simply replace one of the front stock screws by a stud.

Even though this picture is from a Stutzen, the same technique can be used for the 34 and other DIANA's with side mounted stock screws.

As you can see, it is not difficult to sling an airgun, you just need to be a little ingenious.

:-)

Keep well and shoot straight!






​HM

DISCLAIMER;

First of all, an apology. Steve and I started exchanging more and more information and I got carried away on a tangent. He was kind enough to "call me back on track". Perhaps I am too much of a scientist and love bare truth too much. So, I need to rely on good friends to make me see the forest, as I am too entangled in the trees; the delay is mine and mine alone.

What follows are my own personal observations, conclusions, and hopes of further work.
I take full responsibility for what I say or write. If someone demonstrates me that I am wrong, as I have done in the past, I will stand corrected.
Nobody's "Purfect".

Let's re-cap: the FOCUS of this series of articles was the Harmonics Tuner (HT); a relatively simple device that allows the shooter to tune a gun to the best possible performance of a given pellet in the gun, WITHOUT altering the MV.
​
The idea was to compare the performance of the HT under two completely different powerplants to see if there was ANY measureable improvement from both, as different as they are.
As you can see from the results, there is. Smaller or larger, but there is a measureable improvement.
This is what I feel is most original.
Typical airgun tuning is done through cutting coils, change of springs/guides, change of pellets, and adding or removing washers that go from full sized spacers to paper thin power adjusters. BUT that means altering the trajectory (because MV changes) so that accuracy can be obtained.
The HT, in a way and within reasonable limits, allows us to "have our cake and eat it too"; because we can select an MV (obviously within the stability range of the pellet we want to use, and assuming that the barrel does not deeply dislike the pellet), and THEN tune to optimal accuracy and precision (depending on what we want to do with the airgun) to the best possible results within that system.

I have also received "questions" about the validity of using 5 shot groups as "data points" being that sometimes variations between groups are as large without any change, as they are when performing small changes. As limited as our tests were, we are confident that the results are reproducible in any individual's airgun, as long as the proper procedures are followed. 
​The RESULTS for individual guns may be different (as is normal with most aspects in airgunning), but everyone can find an "optimum spot" for harmonics tuning.
​That is part of the essence of the beast.

So, having clarified all that, let's get going

We might make some tweaks still, as this is a pre-production model.
​We are working on making the HPM available as an after market part for ALL 54's (as usual, in good DIANA tradition, it will be fully compatible with all previous editions of the 54, though the T01's may need a little gunsmithing).
I am told that the stock will be available in several colors and that also more traditional Beech (and perhaps some Walnut) stocks will be made available. It all depends on the wholesalers, so if you are interested, write to your favourite wholesaler to request some attention to the point of your interest.

Steve and I have been exchanging a lot of interesting information, and I have also been receiving results from the Harmonics Expert, such as this:

So, I will be writing another entry, this one dedicated to a more detailed and better analysis of what TRULY happens with the spring-piston shot cycle, what determines the efficiency, what are common misconceptions about it, and analyzing more in depth the "phases" of the shot cycle.

Just to give you an advance taste:
The curve above belongs to an ASP 20
You can clearly see that the first acceleration spike (red oval) is where the piston reaches the end of the air compression run, and that a few msecs later (green oval) there is an even greater "slam" BUT, the human senses cannot detect it.
You can also see the 70 g's force vibrations developing during the time of the pellet in the barrel (-20 to +50 g's for 7 msecs, though the dwell time of the pellet in the barrel is shorter).

It takes relatively sophisticated instruments to detect and measure them, not only in magnitude, but also in time. The chart also shows a good, long decaying vibration pattern (blue square).
And all this from a gas spring gun that has been reported as a "smooth shooter" and excellent at bench rest.
¡Surprise!

Anyway, it will be fun to actually make the real behaviour of the shot cycle evident for different airguns. And to see what works and what does not work, independent of what shooters "feel".

Conclusions:

The HT is a device that has been tested and proven in different power plant designs and has proven its value.

​DIANA will include it in the next " edition" of D54 rifles.

There are still other technologies that await research; as long as there are people that are fascinated by the spring-piston airgun, whether it is a steel spring, or a gas ram, there will be things to discover and improve.
And THAT is also part of the magic of airgunning.

Again, I need to thank Steve for his excellent participation and impeccable work. It has been a great pleasure working with him on this.
And also thanks to our readers because without dedicated airgunners willing to read a LONG, FOUR part, entry our words would be like the sound of a tree that falls in the middle of an empty forest . . .

Keep well and shoot straight!






​HM

N.E.
For those of us that remember B&W TV, "B" Westerns, and were raised on a visual diet of clear-cut good and evil as white hats and black hats, the name 'Dragnet' will always recall Det. Sgt. Joe Friday.
And badge # 714 will always mean dedication to the truth and unswerving loyalty to the Law.
Among its most famous phrases:
"All we want are the facts, Ma'am"
In honor of such a simple, unswerving, and devoted to service attitude, we decided to title this entry.
​
Take it away, Steve!
​

​As promised, I wanted to provide you with more in depth detail and comparisons between the two power plants that were used in the recent Harmonic Tuner testing.  

I mentioned in that write-up that after recrowning the barrel on my 56TH, Hector completely assembled my barreled action with some of his own components and returned to me for  testing.  It arrived with one of Hector's Short Stroked HMO powerplants, a tuned T06 trigger and the most beautifully detailed Diana 54 stocks I have ever seen! He went all out on this set up provided to me for testing.

We have already seen the rifle in action during the Harmonic Tuner testing.  Now lets turn our attention to the powerplants,  beginning with the Short Stroke HMO set-up.

28mm x 76mm HMO Short Stroke

The set-up as provided to me included everything you see pictured below;

Compression Tube with Reinforced Breech Seal
HMO piston
Main Spring with dual guides
Cocking Handle with modified fulcrum and linkage extension

It was set up for my requested energy level (11.2 to 11.4 fpe range)

​The HMO piston is a work of art with an o-ring main seal, nylon top cap, and a rear guide that is nicely machined to ride solidly inside the action, an improvement to the flared out piston skirt on factory pistons. 

You can also see the dual spring guide set-up.  This includes a conventional guide that inserts into the main spring, and an outer guide that surrounds the spring.

​Looking at the Transfer Port you can see the seal has a center reinforcement collar measuring approximately 3mm ID.

​The piston weighs in at about 317 grams.

​Inside the outer spring guide are the preload spacers, one of which appears to be a softer compound anti-bounce washer.  It is the blue washer in the picture below.

​I mentioned the "Modified Fulcrum" on the cocking handle.  Here is a close-up showing the re-positioned cocking linkage pin.

​The linkage rod end is solidly supported with nylon washers on either side for a smooth cocking stroke.

​To account for the relocated pivot point, the linkage rod has a threaded extension added.  In this picture you can see a factory linkage rod (bottom), alongside of the modified cocking linkage (top)

​It is evident that Hector has done his homework on this set-up.  It is precise, consistent and was easily tuned on target using the harmonic Tuner.  The cocking stroke is extremely light and will have you questioning whether or not your are truly making over 11fpe.

After all testing was complete, I purchased this set-up from Hector.  It is well made, durable and easy to tune on target.  I was able to successfully tune to sub 3/16" c-t-c 5-shot groups across two series of tests at 32 yards.
​
AGT 22mm x 96MM Skirtless

This set-up has been covered in much greater detail in a couple posts I have made on GTA and AGN, but I will give a quick overview;

This set-up consists of a factory Compression Tube sleeved down to 22mm.  The transfer port retains the factory 4.1mm ID.

The piston uses the factory piston rod, and has a dual seal piston affixed on the end.  The dual seals consist of a parachute seal and an o-ring main seal, and help reduce the effects of temperature changes on your velocities.  The piston also has two supporting guide bearings, with a special top hat that also functions as a third support bearing.

This is an exceptionally smooth powerplant and was producing groups as small as 1/4" c-t-c at 49 yards.  It is also very well made, solid and durable.  Adjusting preload can be done without a compressor.  I am able to compress the trigger assembly into place with one hand and insert the trigger block pins with the other hand.

​This piston weighs in at 149.5 grams

​In addition to the mechanical and dimensional comparisons, I also set up a test to measure the cocking effort for each set-up.  

This was accomplished by taping a Protractor above the Cocking Handle, centered directly over the pivot point.  The rubber grip cap was removed from the cocking handle and a slotted wooden block was inserted inside the end of the handle.  The block was supported by rubber sheeting, and had a groove in the center.  I then looped a wire tie around the handle, centered in the groove.  The rifle was supported firmly in a padded support and measurements were taken using a digital scale. 

The weight measurements were taken at specific locations in the cocking stroke, with the max reading being recorded just before the piston rod contacted the trigger mechanism.  Due to the differences in cocking stroke length across the power plants, the max readings were not the same as you can see in the chart below.

The pull point was centered right where you would place your hand when cocking the rifle and scale was kept inline with the direction of pull.

Here is the set-up for testing:

With the barrel crown issue now resolved, we moved to the next step in this project which was the HT (Harmonics Tuner) installation and testing.  

With the rifle set up, Hector conducted his own series of tests just to verify what setting it would prefer on target.  Once complete, he reached out to me to see if I would be willing to continue with this testing.  Hector said that he would like to keep the rifle set up just the way he had it for my first phase of testing.  After discussing the terms of this testing I agreed without any hesitation.

A few days later the rifle arrived.  For this testing you would think that the equipment would consist of an old beat up stock and parts that were laying around in Hector's shop.  After all, it would be packaged and shipped to my shop, plus be assembled and adjusted throughout the testing, and finally disassembled packaged and shipped back to Hector.  

Much to my surprise when I received the package, I found an exceptionally well packed rifle in a padded hard case, with precisely cut out areas for each item.

Included were a Vortex 6-24x50 Diamondback Tactical, a custom parallax adjustment wheel, an accurized ZR mount, and the most beautifully detailed D54 stock I have ever seen.  Wrapped over the stock was a padded leather cheek piece...very nice!  

​Inside the back it looks like a nylon collar machined for an exact flush fit to the end of the muzzle with zero o-rings added

​Adjustments are made by adding or removing o-rings.  Adjustment range is between 0 and 10 o-rings.  Simply loosen the 3 set screws, slide the HT off, add/remove o-rings, reinstall HT and lightly snug the set screws.

​Here is a view from the front of the HT.  I think this picture was taken with 9 o-rings installed.

Now let's talk about the arrows:
​While I was doing this chart I saw a pattern to both tests that I did not notice before.  Both tests have a sort of rolling pattern to them where the groups gradually increase, then decrease in size, and then start over again.  Look attentively at the arrows in the chart above.

Ignoring the normal group to group variation that you would expect to see when shooting consecutive groups without making any changes, you can definitely see these patterns.

It looks like the 28mm set-up has a more pronounced climb from smallest to largest group sizes, and the 22mm has a less pronounced climb.  This was reflected in my article and supported by the data.  However, in the 0-10 o-ring range of testing, the 22mm had three cycles of this pattern, while the 28mm had only two.  In my opinion this supports the theory of increased frequencies being produced by the 22 mm's kits. 

The 28mm generates higher harmonics (as shown in the greater spreads from smallest to largest group sizes), but lower frequency (only 2 complete cycles of small to large groups in this testing)

The 22mm on the other hand made three complete cycles in this testing, indicating higher frequency.  The peaks and valleys (group size differences) were lower so the harmonics were not as pronounced, but it occurred more frequently.

So, looking at this chart, I would bet that the targeted ranges for o-ring settings should be similar if you target the valleys (smallest groupings).

For example, on the 28mm the best settings could be either 0 o-rings or 9 O-rings (at this exact set-up, velocity, pellet, etc).  A slight change to the set-up would require a new test, but results should be similar with 2 specific settings being revealed in the range of 0-10 O-rings.

On the 22mm set-up, you should find 3 valleys across the range of 0-10 O-rings due to the increased frequency of the harmonics.

This is VERY interesting!!  I am theorizing that tighter groups in both tests would relate to the barrel being tuned to match an end point of muzzle movement with the release of the pellet.

​Testing summary;

28mm x 76mm HMO Short Stroke

The HT was very effective in tuning the 28mm x 76mm short stroked powerplant. You could see dramatic changes in group size with even the slightest change in HT settings.  The size difference between the largest and smallest group was .512".  
You could also clearly see when you were in the sweet spot ranges for the tuning (1-4 o-rings, and 8-10 o-rings).  This powerplant did not like the range of 5-7 o-rings.  This would be in direct relation to the barrel harmonics when using this particular powerplant, and at this particular power setting.

AGT 22mm x 96mm Skirtless

While I could see slight changes across the adjustment range of the HT, the overall effects of the adjustments were less.  There is no doubt that a sweet spot could be found for dialing in for the smallest group, but the size difference between the largest and smallest group was only .312".  

Further experimentation will be needed on the 22mm set-up.  Now that the crown issue has been addressed, I will be following up with group testing using both the HT and the factory muzzle weight.  This particular powerplant may very well prefer the added heft of the factory muzzle weight.  Previous testing revealed .25" groupings at 49 yards on this set-up using the factory muzzle weight.

I hope you found this HT Testing interesting and helpful.  

Up next will be an article that focuses on the two powerplants and some of the differences between them.


Steve