Does anyone know what the velocity difference between a 16", 20", 22" &24" barrels are?  I would like to build a varmit rifle and I know what what length of barrel to get?

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Mike

Actually,  Barrel length does not matter much on velocity,     The only way to really test this theory is to use the same barrel and cut it shorter and shorter.   I have 7mm Rem mags,  1 is a shaw,  1-9.5 twist,  the other is a Shilen 1/9 twist.   The shilen is 26", the Shaw is 24".   You would think difference?  No,  With identicle loads the shaw burns abot 50fps faster than the Shilen.  So does barrel length matter?  hmm nah  I stopped belevin that when I chrono'ed my two 7mm's.   That being said,    in a gas gun it might due to where the gas bleedoff is.  Its my understanding that middy's get higher velocity than carbines,   since it has 2 extra inches to build up preasure I can almost see this but not sure,  Just got done building my middy,  so will compare it to my carbing and see.   Both have 16" SST Barrels,  just diff gas hole locations.  

Barrel length DOES matter, but sometimes we mistake a difference we can see on a chart for one we can see in the field. I don't think that a 26" barrel is worth the length and weight it has over a 20" barrel. I fact, I might consider a 24" barrel for a prairie dog gun, but my preference for basically everything is 20" or less. You get what, 120 FPS going from a 20 to a 26 inch barrel? An animal or human won't notice the difference. Trajectory is minimally affected.

16" loses appx 200 fps from 20".

11.5" loses appx 600 fps from 20".

Jeez where do some of you guys get your info?

Barrel length DOES matter.

Shorter Barrel tests here