Air Gun Home :: View topic - Hatsan AT44S-10 Long in .25 cal

rsterne · Moderator

Many thanks to sniper (Dan) for his speedy delivery of my new winter project.... What a BEAUTY!!!....

I got the Air Stripper and a full power valve stem as well.... plus a new Leapers 4-16 x 40 AO IR scope which I found I could mount in low rings and still clear just fine.... The gun measures almost 45" long and weighs 9.75 lbs. with the scope....

Hopefully I'll find the time to clean it up and put a few JSB Kings down the barrel before too long....

Bob

Alstone · Moderator & Site Supporter

Very nice Bob I especially like the air stripper it set's it off.

Al

ZipSnipe · Veteran Member

Yes great looking gun!! Yeah sniper is great to buy from, quality stuff!!!!!!

That's who I got my first 1077 from, that thing is a champ!!!

Big Ern · Veteran Member

rsterne · Moderator

I cleaned the barrel with Goo Gone and then shot some different pellets to find out how it does in stock non-PAL form.... Here are the results....

From 200 bar down to 85 bar it delivered over 200 shots (23 9-shot clips) within less than a 6% range.... Dropping down to my standard 4% ES requires filling to 195 bar and refilling at 90 bar and gives 21 clips or 189 shots.... The lightest pellets (17.3 gr. Lasers) shot 450 fps (7.8 FPE), H&N Match 21.6 gr. shot 420, JSB King 25.4 gr. averaged 393 fps (8.7 FPE), Baracudas shot 365, and EunJin Domes went 345 fps.... The EunJin Points were too long to cycle reliably in the magazine, but loaded singly shot 320 fps (9.5 FPE).... The 189 shot string of JSBs used 105 bar of air from the 230 cc (14 CI) cylinder for an efficiency of 1.12 FPE/CI (14.6 barcc/FPE)....

All this gives is a baseline for comparison after I swap out the valve stem for the full power one.... It will be interesting to see the difference....

Bob

rsterne · Moderator

The conversion to full power started today.... Here is a photo of the non-PAL (under 500 fps) and full power valve stems.... They seal on a plastic (Delrin?) seat inside the valve housing that is 0.171" diameter....

The plastic spring seat is pressed into the end of the valve against the large flat end in the photo.... Because it is shouldered and fits flush, it is difficult to remove.... I therefore filed a flat in each side big enough to get the blade of a small flat screwdriver into to pry it out.... as this won't be the last time I take the valve apart....

Here are the port measurements and areas....

Hole in plastic spring seat 0.196" (larger than the ID of the spring)
ID of the valve spring 0.171" (which limits the flow into the valve)
ID of the valve seat 0.171" (area 0.0230 sq.in.)
OD of the non-PAL stem 0.153" (area 0.0184 sq.in.)
Remaining throat area with non-PAL stem 0.0046 sq.in. (equivalent to 0.077" D)
OD of the full power stem 0.100" (area 0.0079 sq.in.)
Remaining throat area with the full power stem 0.0151 sq.in. (equivalent to 0.139" D)
Six exhaust ports measuring 0.105" D each (total area 0.052 sq.in. - over twice what is required)

The conclusion is that (at least in theory) more air can get into the valve through the spring than can get out through the valve throat, which is the limiting factor to airflow in the valve.... From previous experience, the wasted volume of the six exhaust ports and the groove connecting them affects the efficiency, but that is the subject for later experiments.... Later today, I hope to shoot some string with the gun in it's "stock" full power form....

Bob

rsterne · Moderator

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....

Bob

rsterne · Moderator

This thread is moving over to the "Rifles" section now that it is progressing into the modifications....

http://airgunhome.com/agforum/viewtopic.php?t=8657

Bob