How to increase muzzle velocity
I’m new to this forum and would appreciate any advice you guys might give me.
I bought a Vulcan Tactic 25cal in June. Have put about 600 pellets through it and cleaned the barrel four times. I got it for pest control (raccoons) though it is fun to shoot. I like the carbine-like size, great trigger, looks nice. I’m getting 1/2 inch groups at 40 yds. I’m getting about 887 fps on the chrony shooting JSB Exact Kings 25.39. I would like to see if I can improve the group size by increasing the muzzle velocity to 910-920 fps by adjusting the HS. I don’t want to mess with the regulator at this point.
I removed the gun from the stock. Inserted the proper sized hex key in the lower screw in the back, just behind the HS. I assume one would turn it clockwise, inward, to increase the velocity. Is this correct? However, neither a full turn clockwise (inward) nor a full turn counterclockwise (outward) from the starting point seemed to make any significant difference in the measured velocity. You can’t turn it too many times either way in or out.
Is this the correct procedure. Any advice would be appreciated.
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I appreciate the advice from everyone. I will probably just leave things as they are, the gun seems to be shooting well.
But just for my own knowledge: Is that how you would change the hammer spring tension? Simply putting a 5mm Allen key into the knob behind the hammer spring and turning it, no set screw or lock screw to unlock first?
1/2 inch at 40 yards is good, 1/2 inch at 75 yards is great. 1/2 at 50 yard is a safe bet to strive for. I too would agree that another 40 FPS is not worth tinker for UNLESS is improves your grouping, whether that be up or down in FPS. :geeks:
Oh and when i turn my HST knob 1/2 a turn will move my FPS about 10-15 FPS.
My new Vulcan is doing around 910 fps with JSB Kings and is giving 1/2″ groups at 50 yards. I feel that it goes off reg at 140 bars. Though having more power is fun but it it all about the accuracy. Power is useless without accuracy. A friend is shooting his Royale 500 at 810 fps with JSB kings as that gives him 1/2″ groups at 75 yards. My honest suggestion is that if your gun is shooting great then don’t even think about messing with it.
The regulator is maxed out on the Vulcan .25. Increasing the regulator pressure will not increase the velocity. What you need is a heavier HST spring and or decrease the valve tension. I have been able to get the Vulcan to shoot 940 with the tweaking these two items.
I don’t see why extra 40fps would be worth wrecking your gun.
learn the aimpoints, airguns don’t shoot to where the crosshairs meet (like all stupid people do on youtube) that’s my advice.
aha if it wont group, I doubt 40fps will make any difference.
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There is no lock screw. Just make sure you are turning the right hex screw our of two present on the back. Hammer spring tension is addjusted by the one closest to the stock.
After reducing valve tension and reg set at 120bar on my .22, now I can set speed/power anywhere between ~210 fps to 870 fps for jsb heavies just by manipulating the hst screw. Using a weaker, meant for sub-12 ftlb spring though.