Mikey Mon May 03, 2010 6:21 am
I have some data and some graphs of my own making, but its so incomplete its unfair to draw any conlcusive info from it, as there are many other factors to take into account such as cylinder size and porting, spring tension, BB weight.
It does however point to a fairly good rule of sorts:
FPS IS directly proportional to barrel length AND spring power UNTIL the length of barrel matches the porting of the cylinder, at which point any further increase in barrel length has NO additional effect.
A tightbore makes a little difference to FPS
A significantly overlong barrel will noticbly reduce FPS.
Lighter BB's gain more from a longer barrel than heavy ones.
For what its worth, heres the results from my M4, which was the most consistent gun tested.... draw your own conclusions
gun barel brand length 0.12 0.2 0.25
M4 MP5k 110mm Galaxy 110 250 230 220
M4 std cqb 273mm G&P 273 412 349 313
M4 Tightbore 404mm Systema 404 479 368 345
M4 AK47 455mm JG 455 470 367 339
M4 G36 509mm SRC 509 479 368 343