Just happen to remember that during the Korean grabass, they changed the standard one wire recoil spring to a twisted two wire spring in the AN-M3 20 mm aircraft cannon to gain more inertia when loading the first round by releasing the hydraulic charger. I was on the ground and can't imagine what temp the a/c were operating at, but must have been in the high minuses. I know I saw a mechanic trying to pour oil in a 6by6 and it was thick as light grease. The Navy also changed to an anti-freeze hydraulic fluid in the F9F A/C gun charging system.
I'm trying to figure out why the twisted two wire coil spring was selected. Would it be stronger or would it be faster? Scuttlebutt was that it was faster. Was the two wire spring stronger or faster in a sub-zero environment?
I just changed a hammer spring (coil) in a Stevens M 311 which measured the correct length but wasn't strong enough to bust a cap. I don't know the correct weight of the spring but do know the correct length and it was just as difficult to put back in.
I know I have switched from our original subject of slow functioning magazine springs to fast functioning hammer springs but I remember something in physics about a relationship between velocity and momentum. Is it possible for a spring to retain its' weight and still be too slow to maintain desired momentum? Would a twisted two wire coil overcome this loss of speed? I have seen this phenomenon in leaf springs in Columbia shotguns where the spring is still strong but loses its' speed apparently. Any spring experts care to comment? Isn't there a twisted two wire spring in an AK or SKS? I believe there is, but probably for design reasons, not for speed retention.