Hatsan AT44S-10 Long in .25 cal

[SeanMP]

Whats the pitch and the wall thickness?

I always get the heebie jeebies whenever I think about threading high pressure tubes

[rsterne]

I'll measure it next time I have it apart.... One thing I'm not crazy about is that the threaded area is under pressure, as the O-ring is at the very end.... Can you say "stress riser?".... Just from the weight, however, the reservoir feels "strong like truck"....

Bob

[rsterne]

I got a chance to try a few pellets today in the "full power" version of the gun.... The graph below shows the shot strings for all shots greater than 96% of the maximum velocity for each pellet.... The strings are shifted so that they align with the pressure range which worked for each pellet.... As is typical, the heavier the pellet, the lower the pressure at the peak velocity....



Summary of results (averages given):

Beeman Laser 17.3 gr. - 965 fps (35.7 FPE) - 22 shots @ 1.25 FPE/CI
H&N Match 21.6 gr. - 899 fps (38.8 FPE) - 23 shots @ 1.27 FPE/CI
JSB Exact King 25.4 gr. - 854 fps (41.1 FPE) - 25 shots @ 1.33 FPE/CI
Benjamin Domed 27.8 gr. - 815 fps (41.0 FPE) - 23 shots @ 1.40 FPE/CI
H&N Baracuda 30.9 gr. - 787 fps (42.5 FPE) - 24 shots @ 1.40 FPE/CI
EunJin Domed 35.3 gr. - 750 fps (44.1 FPE) - 26 shots @ 1.36 FPE/CI
EunJin Pointed 41.7 gr. - 707 fps (46.3 FPE) - only fired 3 shots (single load)

It is interesting to note that Hatsan advertise this rifle as 42 FPE, so they are certainly not exaggerating.... Since the primary purpose of this rifle will be varmint hunting at longer ranges, I will concentrate on the pellets best suited for this purpose.... ie the ones with a good Ballistics Coefficient and a decent muzzle velocity for the job.... The initial development work will be done with the JSB Kings, and if I can get upwards of 50 FPE, I will also try the Benjamin Domes, the new H&N 27.8 gr. Baracuda Hunter Extremes, and the H&N Baracudas.... The next step will be to modify the stock so that I can adjust the hammer spring preload without removing it.... Since the pellets I want to test are topping out at 160-170 bar, and the rifle is good to 200.... I will have to increase the preload to take advantage of what should be more power lurking in this design....

This thread is moving over to the "PCP" section now that it is progressing into the modifications.... http://www.canadianairguns.com/showt...S-10-Long-Mods


Bob

[SeanMP]

Interesting string Bob

Right after peak velocity on almost every single pellet there is a drop then a rebound. Whats going on there?

[rsterne]

The gun is "shifting gears" from self-regulating to the downside of the curve?.... I have no idea, really, but it's not uncommon to see certain parts of velocity curves showing patterns.... smooth in one part, ragged in another.... also not unusual to see a low shot followed by a high one (or vice versa).... Since the valve is open to the air reservoir it can't be "retained air" like in a pumper, there must be some other explanation.... The valve poppet closing a bit harder and sticking on the following shot?.... or softer and being easier to open the next time?....

It's an interesting anomaly, but in the grand scheme of things it makes no practical difference as the delta is still well within the 4% overall ES....

Bob