Hatsan Bully 25 cal – 1st tuning round – Found the shot curve

Forums PCP Airguns Hatsan Bully 25 cal – 1st tuning round – Found the shot curve

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    Rich7777
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    Member

    Went out to this range this morning. Thanks IndianaAirguns.com, free air rocks! I started tuning the Hatsan Bully 25 cal. Loaded all 3 mags with  JSB Heavy MK IIs. I filled the Bully to 2600psi, which should be around the top of the shot curve. Then started adjusting the Hammer Spring Tension screw until the chrono read 880fps. Once there, I tightened the grub screw to lock the HST screw in place and put the action back into the stock. Filled to 3600psi and started a new shot string. 

    Here’s the data per magazine (13 shot mags)

    Here’s the shot chart

    Decent results and has a curve in the shot curve! If I only fill to 3200psi and shoot down to 1800psi, I can stay in the 850-880fps range and get 4 full mags (52 shots) in that range. The Bully is growing on me. Next Step is a Huma Regulator.

    Tuning Info:
    The depth from the back of the action to the top of the HST screw is 0.345 inches. I recommend setting it at 0.355 inches. For reference, the screw depth was originally ~0.8 inches which would sling a JSB heavy over 1000 fps.

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    Glem.Chally
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    Member

    Yeah very impressive,  that thing is a hammer and such a gentle bell curve.  Are you expecting to lose some power by regulating?  With that much hammer spring to play with even if it dips you should be able to get it back by more spring.

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    Rich7777
    Participant
    Member

    “Glem.Chally”Yeah very impressive,  that thing is a hammer and such a gentle bell curve.  Are you expecting to lose some power by regulating?  With that much hammer spring to play with even if it dips you should be able to get it back by more spring.


    At 50yd and pellets straight out of the tin, the Bully grouped well at 850-880 FPS. By adding the reg and adjusting HST, I’m looking to start my shot string around 865 to 870 fps and stay at that velocity until I fall off the reg. I don’t mind giving up shot count for tighter groups. This should also shrink the ES and SD across mags. I think I can get 3 full mags (39 shots) at the target velocity. 

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    Hynzie
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    Member

    good stuff thanks for the info

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