Originally Posted by Nik12
That is true. But if the heavier grain bullet has a lesser velocity (even by a bit) it cancels the effect.
You're right... again, AT THE MUZZLE. The muzzle energy WILL be consistent in an AEG or springer.
However, to reiterate, at range, a lighter BB loses much more of that energy due to other forces (namely, wind or standing air).
Have you ever shot BBs through a crosswind? Have you ever noticed how a lighter BB will always stray further than a heavier BB? Now imagine those two BBs shooting straight with no crosswinds, the wind they face head on will affect the lighter BB more than the heavier BB, the same way a crosswind will affect a lighter BB more than the heavier BB. This is the explanation for the comments people have made that "we're not shooting through a vacuum."
Originally Posted by Rob
I suppose this gas gun variable velocity fact is the reason why the WA gigant has such large fps values even on duster; the long barrel means the bb will spend more time in there and thus more gas is expelled.
i can see how this works in a gbb gun, where the gas propels the bb first and then diverted to the blow back function via a valve thingy in the nozzle (WA design for instance), but does this work in nbb guns? the tanaka sniper rifle series has large fps numbers but is that the result of a valve with a set amount of gas coming out or is the gas output variable as in a gbb
This effect is true on almost ANY gas gun - INCLUDING real steel guns. Once the propellant has burned off, the expanding gas is what pushes the bullet forward. Longer barreled guns will have higher velocities than shorter barreled guns due to the greater amount of time the gas has to expand and impart energy on the projectile.
Tanaka rifles have large velocity numbers as a result of long barrels combined with high gas outputs (depending on how wide your PCS bolt is opened or closed.) In wide open, the gas valve opens much wider than any GBB can produce.
The limitation of bolt action or any single-action gun for that matter, is that the gas is only fired for a set amount of time, regardless of the weight of the BB. There is no rocket/floating/reed/power valve to detect the release of the projectile and shut off the gas valve like in self-chambering guns. There is an upside and a downside to this. The upside being that the gas volume output is ALWAYS the same, regardless of the projectile weight. Consistency is key to sniping.
The downside is that there is a potential for inefficient gas use (too much expelled), or the opposite - not as much gas is expelled, which leads to a lower velocity than can be achieved.