fx impact x .25 Cal heavy over 880fps anyone?

[Glem.Chally]

I have ordered a .25 Impact with 700mm barrel and 600 mm .22 kit plus a 600mm .22 B-liner to shoot jsb redesigned pellets. I am planning to achieve 940ish fps in both calibers. Going through this thread I think I'll be able to achieve my target velocity without any mods or will I need to do the modifications?

Thanks.

940ish with what pellet/s?

Ah ok 25.4 in .22 and 33.95 in .25?

Yes the King heavy in .25 and the redesigned monsters in .22

I bet you could, I can get those redesigned to almost 1000 with the Boss with Boss hammerweight in .22 (600mm .22 barrel). Just ran one over the chrony at a pretty hot tune and got 976. I've never tinkered with the Impact however, so just guesses.

Adding the extra length to the barrel would probably get king heavies to 940 or beyond. Might need to play with reg pressure and find the happy place with the hammer spring adjustment.

 

[Karly64]

I totally tuned my fx impact. It was mk1 but I put a mk2 valve and 25% extra plenum fac sprin plus many more tweeks and drilling’s I set my huma reg onto 90bar it is now at 65ft lb and firing 1072fps. I altered the forward control knob and brought FPS down to 944 to tighten groupings very quiet and knocks 31 grain and 40gr out like a dream