Air Gun Home :: View topic - Hatsan .25 cal AT-44S Long with Heavy Pellets

rsterne · Moderator

I recently got some 36 gr. Daystate Rangemaster pellets, so I decided to see how they would work in a couple of my guns.... My Hatsan was capable of significantly more power than the way I had it tuned with JSB Kings, so I pulled off the air cylinder, reinstalled the 0.090" stem in the enlarged valve, and tried them out.... It took a few more turns of preload for the gun to be happy with the much heavier pellets, and I tested them against 35 gr. EunJin Domes, plus the (now drastically overpowered) Kings.... Here are the results with the heavy pellets....

With 8 turns of preload, 2800 psi (193 bar) is the optimum fill pressure, and I got 14 shots within a 4% ES, averaging 68 FPE.... At 9 turns of preload, the first shot with the EunJins was 3% below the peak and I got 12 shots finishing well within a 4% ES, averaging 71.3 FPE.... With the 36.1 gr. Daystate pellets, the first shot was 2.3% below the peak and the 4% ES string was again 12 shots, averaging 72.4 FPE.... By dropping the fill pressure to 195 bar, I can shoot 9 shots (1 full clip) within a 17 fps ES (1.8%), ending at 155 bar.... That works out to a 73 FPE average, and an efficiency of 1.18 FPE/CI.... pretty astounding for that much power.... While 9 shots isn't a lot, I have a 90 CI 4500 psi tank with a 2800 psi regulated output to carry in the field.... By my calculations, that will give me 18 fills, so I end up with a gun that shots at 73 FPE and stays within a 2% ES, one clip at a time....

In terms of accuracy, my initial tests showed that at 32 yards the Daystate pellets would hold groups that could be covered with a quarter.... That's not quite as good as the Kings when kept at about 970 fps, but at that velocity they are only 53 FPE, 27% less power.... I tried the Kings at this setting, and they screamed across the Chrony at 1070 fps (nearly 65 FPE) but their groups were no better than the Daystates.... and both pellets were tighter than the EunJins.... I still have to tune the air stripper to optimize the group size for the Daystates....

While I was testing, I wanted to check the Ballistics Coefficients at this power setting, so I set up the Chrony at 32 yards, and I got the following results....

In all cases, I used 5 shots centered at the top of the velocity curve, to get the most power and the least variation in velocities.... It is interesting to note the when you push the JSB Kings this fast, their normally great BC is starting to deteriorate, even when measured over 32 yards.... If you checked it over the first 10 yards, I think it would be under 0.015.... They are losing a LOT of velocity and energy in the first few yards when you push them this fast.... On the other hand, the 36.1 gr. Daystate Rangemasters have a great BC, and are retaining over 80% of the muzzle energy at 32 yards.... At 100 yards, they would still have over 35 FPE remaining.... The SR12 Reticle on my Hawke 6-18 x 44 scope will be useful to 112 yards (over 100m) at full power with the gun sighted for a 1/2" kill zone (40 yard zero) with the Daystates.... Here is a photo of the finished rifle....

I'm extremely happy with the results.... I ended up with a a real quarterbore powerhouse at 73 FPE....

Bob

Trenier · New Member

Nice write up. Thanks for posting.

rsterne · Moderator

I finally got a chance to let the Hatsan with the Daystate pellets stretch it's legs yesterday.... The results were disappointing.... I couldn't get it to hold 5 shots consistenly under 2" at 50 yards.... I tried with and without the air stripper, and at velocities of 900 and 960 fps, and I even tried some pellets I ran through a rock tumbler for 15 minutes.... If anything the tumbled pellets grouped worse than those straight from the tin....

I also had a problem with the pellets feeding properly.... Although they are about 0.015" shorter than the thickness of the magazine, the center portion is long and straight, and the O-rings won't hold them securely enough.... It was impossible to feed through an entire 9-shot magazine without a jam, and that damaged the skirt on the pellet.... In order to test the accuracy, I had to load 1 pellet at a time and manually index it to load it.... I know that the magazine problem was not causing the rather dismal accuracy....

I suppose with a short range gun I might be satisfied with a gun that will consistenly hit a quarter at 25 yards.... However, this rifle weighs nearly 10 lbs. with the Hawke 6-18 scope and bipod.... and the intention of using the 36 gr. Daystate pellets was to up the power, particularly at long range.... This wasn't in the cards, so I'm going to set the gun back up for the JSB Kings and see how they shoot at or near maximum power, which is well over 1000 fps.... I've already tried a lot of other pellets, and the Kings are the only ones that have the accuracy to compliment the rifle....

Back to the drawing board.... I sure wish I could get a 30+ gr. pellet that would shoot accurately in this Hatsan barrel.... It sucks when a gun is held back from it's potential because the best pellet only weighs 25.4 gr....

Bob

rsterne · Moderator

I went back to the JSB 25.4 gr. Kings today.... I had to turn the hammer preload in one turn, and shot the following string....

1001
1007
1019
1024
1031
1036
1039
1038
1040
1044
1040
1036
1034
1030
1023
1011
1002

That's 17 shots within 4% ES, nearly 2 full clips, peaking at 61.5 FPE and averaging 59.5 FPE.... The gun is back to shooting stellar.... I tried it at 1070 fps, and the 50 yard group was about an inch.... I was very pleased that just one turn on the hammer spring tightened up the groups to the same as the gun shot at 960 fps.... Since it groups like this, I may as well have the extra 8 FPE, even though it costs me a few shots....

50 yards, 5 shots, 0.45" C-T-C, easily covered with a dime....

100 yards, 5 shots, 1.25" C-T-C, backed up by two more groups at 1.37" and 1.45"....

I'm delighted to have my Hatsan back shooting the way I know it can....

Bob