Hatsan .25 cal AT44S-10 Long Mods

[rsterne]

No problem.... 1 turn is 360*....

Bob

[EIEIO]

Hi Have you tested the accuracy down range yet?

[rsterne]

4 year old post, don't even have the gun any more....

Bob

[SeanMP]

Ain't that the truth

[rsterne]

Got some time this evening to do the testing of the valve with the groove filled in with JB Weld.... As expected, there was a slight gain in performance, but the efficiency has pretty much leveled out.... Here are the results....



The interesting thing about this version is that the performance at mid-preload settings continues to improve.... The best shot strings are now happening at less preload than before.... I got 19 shots within 4% with the JSB Kings, 971-1007-968, averaging 992 fps (55.5 FPE) at 1.13 FPE/CI, filling to 200 bar and shooting down to 133 bar at 6 turns of preload.... The best strings with the H&N Baracudas and the EunJin Domes were at 6.5 and 7 turns of preload respectively, and returned 16 shots....

I shot a few pellets at 8 turns of preload, and the velocities were peaked pretty much at 200 bar for the lighter pellets and 180 for the heaviest.... The maximums recorded were:

25.4 gr. JSB Kings - 1046 fps - 61.7 FPE
30.9 gr. H&N Baracudas - 982 fps - 66.2 FPE
35.2 gr. EunJin Domes - 939 fps - 69.1 FPE
41.7 gr. EunJin Pointed - 881 fps - 71.9 FPE

I think there is a bit more in the gun yet, I could enlarge the valve throat a bit more and slim the stem.... and then I might have to make the inlet side of the valve breathe a bit better as well.... If I do that, I will then have to restrict the transfer port to keep the velocity under 1000 fps with the JSB Kings.... so I don't know if it's worth it....

Bob

[remtom1200]

Well, vacation's over, time to open up my AT44 10/22 again! I am surprised of the results from opening the valve seat bore. This is a great write-up bob, and now I will try and find a balanced combination for my shorter version in .22 cal.

[bruce32466]

Hey guys. Very nice tutorial.
New here. I just completed this entire tune to my at44-10 .22 long but I don't have a chrony to test with but some day I hope to get one. Not sure what to do as all the tests posted in this thead are for the .25 version of this gun.My questions are:
I'm looking to get about 900 ftps using either beeman kodiak 21.14 gr or crossman premeers 14.3 gr. What is the lowest bar level that will achieve 900 ftps in my situation?
I'm thinking about putting a regulator on it and would like to set it to maximise my shot count. What is the best one at this time to get? I'm leaning towards robert lanes on ebay???
Having done this tune, how many turns should I adjust my hamer spring tension to maintane 900 ftps with regulator set at prescribed bar and likewise how many turns should I decide to forgo the regulator? I would hate to have air continue long after the pellet has left the barrel.
Any help is greatly appreciated.
Thanks,
Bruce

[bruce32466]

Thank you for taking the time to give me a good argument against the regulator. As I said, I'm new and do respect your opinion. I have noticed some improvement in power after the mod so maybe just backing the hamer down a little will sufice for now, at least till I can save up for the chrony.
Thank you much for you input.
Bruce.

[Ohio air gunner]

A you tube video of this entire process would be gold literally. Or a video you make and sell I would happily be your first customer .