I have an impact M3 .22 cal 700mm, Sniper Edition, heavy slug liner for high power shooting 34 gr slugs at 200m. It worked reasonably well and lauched the 34 grains @ 922 fps with p Reg 2 = 150, spring tension reading 4.7 and valve fully open: 1 turn after the 4th mark. I got .8 MOA accuracy...