Hi. Are the Gamo igt and Crosman np gas springs about the same length?The np is 10 1/4 in.Crosman has 12 ft lb np's in stock and it would be great if it is a drop in swap.I think a 12 ft lb swarm would be fun for summer get togethers. (Or all year for me.)Thanks!
Don't have a Crosman NP, but do have the IGT.Total length: 9 7/8"Shaft: 4 1/2"Piston body: 5 3/8"
I'm measuring a piston throw of ~4" for the Crosman rifles I have. My NP1 & NP2 shafts measure 4-1/4". Assuming a preload of up to 1/4" is consistent with these measurements.In the TNT (and IGT?) rifle it looks like piston throw is 4-1/2" . My TNT gas spring shaft measures 4-3/4". A preload of up to 1/4" is expected so that is consistent with a measured 4-1/2" piston throw. Short stroking a springer usually reduces muzzle energy which would not be bad in your case since the goal is to reduce muzzle energy to ~12 fpe. However, if the NP reaches maximum physical compression before the Gamo trigger can latch onto the Gamo piston the Crosman NPs will simply not work in the Gamo.I think you might be able get a TNT (or IGT) to work in a Crosman rifle by carefully grinding off any excess shaft length. I just don't see how it will work the other way.https://www.gatewaytoairguns.org/GTA/index.php?topic=166849.msg155885111#msg155885111"Watching"... I'd like to be wrong in this case and see someone make a successful swap of a Crosman NP into a Gamo rifle ;-)Good Luck!edit... If it were my project I'd take some careful measurements, find a suitable coil spring from Vortek, make whatever plastic spacers/guides needed on my drill-press or small wood-lathe, and proceed to cut coils off the spring until I reached my fpe goal. It's a fair amount of work but I enjoy that effort as much as shooting the rifles. The conversion shouldn't require any irreversible changes to the rifle so it could always be returned back to factory specs if the low fpe version does not perform as expected.