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m102404 · October 19th, 2011, 08:49

A M90 or 100% spring should work. Try to avoid cutting down springs as it's very much less than exact.

Since a tightbore, bearing spring guide, bearing piston head and how nicely the internals are setup will all tend to boost your FPS a bit you can hedge your bets a bit and if your m90 spring is a non linear spring (i.e. a Modify sp90 has closer packed coils on one end) you can reverse the spring and put the tighter pack at the front closer to the piston head. That will kill off some FPS as I've regularly seen a sp90 spring hit 340fps in a nicely tuned setup.

As always...a chrony is the only way to know for sure. And the peace of mind of doing that many guns....and then then powering them back up afterwards...will pay for a cost of a chrony right there.

October 19th, 2011, 08:49	#18
m102404 Tys Trader rating Join Date: Apr 2006 Location: Toronto	A M90 or 100% spring should work. Try to avoid cutting down springs as it's very much less than exact. Since a tightbore, bearing spring guide, bearing piston head and how nicely the internals are setup will all tend to boost your FPS a bit you can hedge your bets a bit and if your m90 spring is a non linear spring (i.e. a Modify sp90 has closer packed coils on one end) you can reverse the spring and put the tighter pack at the front closer to the piston head. That will kill off some FPS as I've regularly seen a sp90 spring hit 340fps in a nicely tuned setup. As always...a chrony is the only way to know for sure. And the peace of mind of doing that many guns....and then then powering them back up afterwards...will pay for a cost of a chrony right there.