The Hämmerli Pneuma

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