Originally Posted by m102404
Isn't also highly dependant on the stiffness of the bulb/valve spring? Or does this whole thread make the assumption that the stock TM bulb/valve spring is used?
Yes, the spring will affect it as well, but at this point, we're comparing apples to apples here and only looking at the cylinder bulb (for my review anyways.) Amos' original thread was comparing a highly modified 1911 with a Firefly valve to the ARS valve. There is no mention of what other upgrades are in the pistol.
Stiffer valve springs keep the valve open longer, and thus, more gas used and slightly slower closing time.
I only recommend the stiff valve springs for extremely high output/fps pistols, running propane, hi-cap mags, high flow mag output valves, etc. Weaker setups won't be able to close the valve reliably and quickly, which ends up in a lot of wasted gas. Many users who upgrade to the Nine Ball Dyna piston heads and install the spring will experience 30 shots per mag to all of a sudden only 10 shots a mag and have no idea why.