The piston id is pretty average. What's the cylinder bore out of curiosity? What's the distance from the inside face of the piston to the rear of the piston?Did I say pictures would help A LOT?
If the square hole is the sear laltch point, then the stroke is only 3 3/8"...
Quote from: Ronno6 on September 23, 2022, 09:52:06 AMIf the square hole is the sear laltch point, then the stroke is only 3 3/8"...You quoted the Vortek spring at 48 lbf/in., and the stroke at 3.375"If PS = piston stroke, PL = preload (both in inches), and SP = spring rate in lbf/in.Spring energy to the piston in ft. lb. is ((PS+PL^2) - (PL^2)) x SR /24. So, with one inch of preload, that would be ((3.375 + 1)^2 - (1^2)) x 48 / 24 = 36 ft. lb., which would put muzzle energy somewhere in the 12 ft. lb. range. With 2" of preload, that would rise to 49.7 ft. lb. to the piston, nearer 16 ft. lb. at the muzzle.
OK. I may have goofed... again.Here is a pic of the pistonIf the square hole is the sear laltch point, then the stroke is only 3 3/8", and I can indeed use a Crosman NP2 ram..
Remember when you have the liberty to choose the spring ALWAYS choose the largest OD you can fit into the piston. While it is true that springs expand upon compression, it is rare that a spring expands by more than 0.015".AND, unless you know that the spring is made of valve spring steel (usually Si-Va), it is not worth the effort.HTH, keep us posted!HM
Give this palce a call. https://www.airrifleheadquarters.com/page/page/251327.htm
Do you have the stuff to machine a few parts?
A Gas Ram does not require as much preload as a Wire Spring as a start.I've taken Gas ram guns down and rebuilt with no compressor.I'd not suggest trying that with out a good spring compressor!I had one get away from me once. I don't want to EVER go through that again!So I built a Spring Compressor using a scissor jack found in many cars.
I don't trust rings to hold a Spring with a 3 inch preload.But that's just me.I tried that and I have a set of rings showing a near fail so stopped using it.