Hello from Australia
Been reading these forums for tips and advice since I went PCP and I got my .22 Impact M3 600mm ~ 2 years, great gun straight out of the box and I set it up to shoot rainbow lorikeet's on the vineyard(declared pest/vermin in this part of Australia that destroys grape vines and kills native birds).
Found the JSB 18gr Barracuda Hunter to work great @ ~960 fps, and after fitting a CF barrel stiffener and harmonic balancer the gun was super accurate and consistent I was never going back to the .22 LR, even though the Tikka .22 LR was so much lighter than the PCP, when I tried it again it just highlighted how accurate and consistent the Impact M3 was and the large capacity magazine really seals the deal.
So now I though I would try shoot something heavier for the rabbits and rats, so I got a STX heavy liner and some slugs, just fitting the liner and trying to shoot a 27gr + slug yielded pretty low fps even after turning the regs up to 140/120, then 160/140, I was barely getting 800fps with the 27.5 nsa .218's and 700 something with the 33gr zans. With the 23gr slugs I could get high 900...
After much reading of forums and watching YT etc it was clear I needed other upgrades !, so I ordered the slug power kit with the tungsten hammer and pin probe and Huma 2nd reg, then after more research worked out that to make the 14g hammer work I needed a lot more pressure so I ran the gun up to 180/165 and didn't really get the speed with the 33+ gr slugs, the gun was getting belted and air usage was extreme, tried the different springs and ball etc, still couldn't get heavy slugs moving and even the speed on the 23gr slugs wasn't much better with all this extra pressure !
Maybe the 14gr hammer is not right for this set-up, so I turned up a brass hammer that weights 8.35g and dropped the 2nd reg down to 140, now I was getting more consistent speeds about the same as the 14g hammer and 160+bar, gave up on the heavy slugs(wow did I go through some ammunition AND air !!) and needed to have the gun useable in the field again so focused on getting a good tune with the 23gr slugs.
I got the 23gr's going 1050 fps + with the regs dropped to 140/120, then sighted and tuned the harmonics etc until I got same speed shot after shot and good accuracy at 1040 fps.
TLDR:
How do I get at least 950fps, preferably 1050fps with a 33gr + slug in this thing !? Is my barrel too short @ 600mm ? Are these internet stories of 1000+fps 40gr .22 slugs fairy tales !?? Do I need even more extreme pressures ?
For me the ballistics of only getting 800fps out of a 33gr slug aren't good enough to bother using this gun for rabbits and rats(need projectile weight to punch through trees etc), its way sub par to a .22 lr with good ammunition doing 1050fps with a 40gr projectile.
PS : this is the late M3, already has power plenum etc std.
Been reading these forums for tips and advice since I went PCP and I got my .22 Impact M3 600mm ~ 2 years, great gun straight out of the box and I set it up to shoot rainbow lorikeet's on the vineyard(declared pest/vermin in this part of Australia that destroys grape vines and kills native birds).
Found the JSB 18gr Barracuda Hunter to work great @ ~960 fps, and after fitting a CF barrel stiffener and harmonic balancer the gun was super accurate and consistent I was never going back to the .22 LR, even though the Tikka .22 LR was so much lighter than the PCP, when I tried it again it just highlighted how accurate and consistent the Impact M3 was and the large capacity magazine really seals the deal.
So now I though I would try shoot something heavier for the rabbits and rats, so I got a STX heavy liner and some slugs, just fitting the liner and trying to shoot a 27gr + slug yielded pretty low fps even after turning the regs up to 140/120, then 160/140, I was barely getting 800fps with the 27.5 nsa .218's and 700 something with the 33gr zans. With the 23gr slugs I could get high 900...
After much reading of forums and watching YT etc it was clear I needed other upgrades !, so I ordered the slug power kit with the tungsten hammer and pin probe and Huma 2nd reg, then after more research worked out that to make the 14g hammer work I needed a lot more pressure so I ran the gun up to 180/165 and didn't really get the speed with the 33+ gr slugs, the gun was getting belted and air usage was extreme, tried the different springs and ball etc, still couldn't get heavy slugs moving and even the speed on the 23gr slugs wasn't much better with all this extra pressure !
Maybe the 14gr hammer is not right for this set-up, so I turned up a brass hammer that weights 8.35g and dropped the 2nd reg down to 140, now I was getting more consistent speeds about the same as the 14g hammer and 160+bar, gave up on the heavy slugs(wow did I go through some ammunition AND air !!) and needed to have the gun useable in the field again so focused on getting a good tune with the 23gr slugs.
I got the 23gr's going 1050 fps + with the regs dropped to 140/120, then sighted and tuned the harmonics etc until I got same speed shot after shot and good accuracy at 1040 fps.
TLDR:
How do I get at least 950fps, preferably 1050fps with a 33gr + slug in this thing !? Is my barrel too short @ 600mm ? Are these internet stories of 1000+fps 40gr .22 slugs fairy tales !?? Do I need even more extreme pressures ?
For me the ballistics of only getting 800fps out of a 33gr slug aren't good enough to bother using this gun for rabbits and rats(need projectile weight to punch through trees etc), its way sub par to a .22 lr with good ammunition doing 1050fps with a 40gr projectile.
PS : this is the late M3, already has power plenum etc std.
