wanted: power-tuning instructions for the Pneuma/Hatsan AT44

[darryl]

Hi gang,
I'm having an awful time finding a (the) definitive instructions for power-tuning the Pneuma. Can someone direct me to a proper link? My searches have yielded unsatisfactory results.

Also, are the parts for the 10-shot version and the single-shot version interchangeable? May want the option to configure both ways. Sometimes I feel like a nut. Sometimes I don't. This is just an exploratory question.
thank you,
darryl

[rsterne]

There is little point in trying to thin down the valve stem more on a full-power (ie 30 FPE) AT44.... The air can't get into the valve fast enough for additional gains.... The easiest and most effective way to more power is to increase the hammer spring preload.... That means backing out (CCW) the adjusting screw found inside the hammer.... You will find that with medium weight pellets the air consumption increases much faster than the power past about 2 turns out.... Check out my results in the chart below....



If you use heavy pellets, you can go to about 4 turns out without using rediculous amount of air....



The columns in bold were where I found the best balance between power and shot count / efficiency.... There is no difference in tuning the single shot or repeaters....

Bob

[darryl]

Hi Bob,
I should have been more specific. I want to turn the power down. And I'm not sure about the need to do that. I'm just trying to find a cure for really bad accuracy. Those RWS Superdomes which seemed to do so well in my basement make ridiculous large groups at 30 yards( how about: can't hit a 1x1.25 dayglo sticker at that range?). Same for those 5.53mm JSB Jumbos and Jumbo heavies (5.53mm x 18.1grains).  This rifle is scattering every pellet I put in it. Cleaned the barrel. din't take the barrel out to shove a pellet through it yet. I think I'd rather send it to Umarex and have them sort it out.   Guess I got a bad one.
darryl

[rsterne]

The easiest thing to do which lowers the velocity very slightly, increases consistency and efficiency (shot count) is to plug the bottom three holes in the valve.... Find out which hole is on top when you tighten in the air reservoir, plug the opposite one and the one on each side of that with small screws or JB Weld Epoxy.... You can't reduce the hammer spring setting as they are normally set at the bottom, although I have heard there might be a spacer under the screw but I never had the hammer out to check, just adjusted it from the back....

Check the crown, the leade in the loading area, and the magazines to make sure there are no burrs....

Bob

[darryl]

thanks Bob,
I did look at the crown, and it looked uniform and smooth, but I don't know enough to be able to be definitive about it.I'll check the magazines too. but I'm thinking of contacting Umarex on this one. Again I saw within one magazine two different POIs.  Really weird.
darryl

[darryl]

Well brush my teeth and call me Smiley  ; it's the magazines causing the problem. The rifle shows consistently tighter groups when I manually load the pellets versus using the magazines. I had to make a simple cardboard single-shot try to load them, but that worked out and I was able to start using the rifle to it's potential (at least in my limited testing.). Nothing wrong with the barrel. The magazines somehow are causing the pellets to be distorted when they're being loaded, and so they spray about. I've written to Umarex and asked for some outside-the-box thinking. I don't want to send the rifle in due to faulty magazines.
thanks guys,
darryl

[tkerrigan]

I tuned up my magazines with cravex rubber abrasive points on a dremel tool and rolled up fine sand paper.  There was lots of casting flash in them.  Regards, Tom

[mtbdrew]

I remember seeing a post on here when I first joined regarding magazine issues with this gun. Might want to do a search in the PCP section as I don't remember the final outcome.

[darryl]

Hi guys,
I had not anticipated a reply after all this time. I sold the rifle either in late '11 or early '12 due to accuracy issues. I definitely did not see the groups others reported at 30 and 50 yards. Mine was a scatter- gun comparatively. thank you for replying anyway,
darryl