I have shot one or two Vulcans that shot beautifully at our Boinger Bash meets. Most notably Speedmaster's last year. It had been fettled; fettler unknown.

I think it has so, so much to do with the spring. Not to be viewed as a "mere" piston propulsion component. Everything revolves around the spring......force unlocked, force cocked, force at point of piston bounce, preload, rate.