Barrel length vs bullet velocity

Enthusiastic_Amateur

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May 24, 2010
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If a .308 manufacturer claims their bullet has a velocity of 2920 f/s from a 30" barrel, what would be the approx velocity from a 24" barrel ?

I don't have access to a chrono and searching the web I've found a load of articles (some of which are pretty old & I suspect date improvements in ammunition) which point to different results which range from 8 f/s per inch up to 50 f/s per inch between 22" to 30".

I appreciate there might be other factors to consider but I'm just looking for a reasonable estimate. Thx
 

ORD

Montani Semper Liberi
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Nov 12, 2005
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Re: Barrel length vs bullet velocity

First...buy a chronograph or find a friend who has one and borrow it. That is the only way that you'll ever be certain of the MV you are getting from your rifle/barrel with any particular ammo. Anything else is just speculation/"best guess." There are just too many variables to factor in to the equation to give you anything more than a guess.

That said, my experience is that you'll lose approximately 25fps/1" of barrel loss. Or...150fps total when going from a 30" to a 24" barrel. YMMV...
 

skinney_7

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Re: Barrel length vs bullet velocity

I ordered a custom upper for a guy who wanted a 26in barrel but they only had a 24in upper instock, not sure if the manuf. wanted to move the 24" upper or what, but he told me once the bullet passes the gas hole (port) the velocity doesn't change that much because of the gas exiting, i could see your velocity may not increase as much as a bolt gun with no port and longer barrel, or the guy could of been completely full of it, i have not chrono'd any 20-24" gas gun barrels with the same load, just a story.
 

LoneWolfUSMC

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Re: Barrel length vs bullet velocity

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TJ.</div><div class="ubbcode-body">If a .308 manufacturer claims their bullet has a velocity of 2920 f/s from a 30" barrel, what would be the approx velocity from a 24" barrel ? </div></div>

There is no way to tell.

My pet load runs 2630fps or so from my 26" M700 with the factory barrel. The same load runs almost the same speed from my AR10 with a 20" Noveske. Yes the Noveske is a "fast" barrel (lapped and polygonal rifling).
 

jakhamr81

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Re: Barrel length vs bullet velocity

Obviously every round is different, I have read in a few articles that a 308 requires 20 inches of barrel length to completely burn the propellant. If this is true then you would not lose any velocity going from a 30 inch to a 24 inc barrel, you actually may have an increase due to not having an extra 6 inches of barrel to pass through. Check out this article written by a sniper instructor at GPS.

http://www.sniperschool.com/sniper-rifle-barrel-length

or this one

http://www.tacticaloperations.com/SWATbarrel/

Still use a chrono.
 

akjaeger

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Re: Barrel length vs bullet velocity

I have a LRB M-25 with a 22" Criterion barrel on it, it shoots my handloaded 168 SMK's @ 2575fps.
My Springfiel Armory M1a "scout" with an 18.5" bbl shoots the same loads 2480fps