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Thread: Hatsan AT44S-10 Long in .25 cal

  1. #1
    Moderator rsterne's Avatar
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    Hatsan AT44S-10 Long in .25 cal

    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
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal:
    .177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 22XX PCP 8-shot Carbine, 2260 PCP Rifle (50 FPE), Hayabusa PCP, .22 B-26, DAQ .308 Exile

  2. #2
    Senior Member SeanMP's Avatar
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    Niiiice!

    I would love to get my hands on a Hatsan. Put it through the wringer washer and see what pops out the other side
    Sean

  3. #3
    Moderator rsterne's Avatar
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    My thoughts exactly....

    Bob
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal:
    .177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 22XX PCP 8-shot Carbine, 2260 PCP Rifle (50 FPE), Hayabusa PCP, .22 B-26, DAQ .308 Exile

  4. #4
    Moderator rsterne's Avatar
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    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
    Last edited by rsterne; Jul 28 2012 at 08:16 PM.
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal:
    .177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 22XX PCP 8-shot Carbine, 2260 PCP Rifle (50 FPE), Hayabusa PCP, .22 B-26, DAQ .308 Exile

  5. #5
    Senior Member SeanMP's Avatar
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    Now that is a beautiful string.

    Hatsan has got their mechanics figured out very nicely.

    How was the out of the box accuracy?
    Sean

  6. #6
    Moderator rsterne's Avatar
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    I really have no idea about the accuracy.... I was just shooting indoors through the Chrony.... One ragged 9-shot hole of varying sizes at 20 feet, when shooting quickly a clip at a time.... I hope to swap out the valve stem tomorrow if I have time....

    I should mention that each velocity plotted was the average of the 9 shot string.... Typical SD per string was about 2.0 +-.... Only a 5 bar (72 psi) drop for each 9 shot clip.... ie 8 psi per shot.... The .25 cal gets a few more shots from 230cc than the .22 cal gets from 180cc....

    Bob
    Last edited by rsterne; Jul 25 2012 at 09:21 PM.
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal:
    .177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 22XX PCP 8-shot Carbine, 2260 PCP Rifle (50 FPE), Hayabusa PCP, .22 B-26, DAQ .308 Exile

  7. #7
    Senior Member remtom1200's Avatar
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    Nice looking setup you have there! I prefer lower mounts for my scopes only couldn't find ones that would work at the time for mine so went medium. The chart I suspect will be very different with the full power stem installed, and I think they used to call it the difference between night and day..lol.
    For every mile of road, there's two miles of ditch

  8. #8
    Moderator rsterne's Avatar
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    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
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal:
    .177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 22XX PCP 8-shot Carbine, 2260 PCP Rifle (50 FPE), Hayabusa PCP, .22 B-26, DAQ .308 Exile

  9. #9
    Senior Member SeanMP's Avatar
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    what does that valve screw into ? The tube?
    Sean

  10. #10
    Moderator rsterne's Avatar
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    Yes, the valve is mounted in the air reservoir.... If you look in the photo just under the knob for the magazine release you can see a brass ring on the reservoir.... That is the largest OD of the valve.... It is sealed to, and removes with, the reservoir.... The small end of the valve is where the annular groove and exhaust ports are, between two O-rings.... More photos to follow....

    Bob
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal:
    .177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 22XX PCP 8-shot Carbine, 2260 PCP Rifle (50 FPE), Hayabusa PCP, .22 B-26, DAQ .308 Exile

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