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.
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.
