18.5" .308 Barrel vs. 20"

wmfirefighter

New Hide Member
Jun 7, 2018
35
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#1
Which of these two barrel lengths would be most advantageous for both competition shooting and hunting and why? Would a longer barrel be better? If so, why? Thanks in advance for your input!
 

wmfirefighter

New Hide Member
Jun 7, 2018
35
1
8
#4
1.5 inches of barrel is splitting hairs. Performance wise, no meaningful difference. Only you can make this decision imo, it’s simply a personal choice.
That makes sense. What about with something like a 22" barrel? Is there a performance uptick with the 22" or maybe even a 24" barrel?
 
Sep 6, 2006
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#5
The difference would be around 150 FPS maybe and would only matter if you wanted to wring out every FPS you could for long distance shooting. Here's an article about barrel length that may help you although this one is using a 6.5 creedmoor.

Effect of barrel length on velocity

No way in hell 1.5” of barrel will lose him 150 fps. In my actual experience, I’d say more like 40-50.
 

fdkay

Gunny Sergeant
Nov 27, 2009
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#6
That makes sense. What about with something like a 22" barrel? Is there a performance uptick with the 22" or maybe even a 24" barrel?
The .308 does quite well out of a 20" barrel.
However, when you consider the velocities involved and the somewhat pedestrian BC's of the typical bullet weights suitable for the .308, longer is normally better.
24" is a really good length, if you aren't running a suppressor. Once you add the 9" of a can to that, it becomes a bit unwieldy.
I really like 24" on my .308, however, my primary .308 gun wears a 20" barrel because it was too damn long with the can on it.

If you are thinking of competing, go 24", if is is going to be a hunting gun, 20" will do.
 

Luke

Sergeant
May 29, 2002
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Colorado
#7
When I cut my Savage .308 from 24" to 18.5" I only lost something like 15fps per inch. You won't be losing much at all going from 20" to 18.5"
 
Likes: spife7980
Apr 1, 2003
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Indiana
#8
When I cut my Savage .308 from 24" to 18.5" I only lost something like 15fps per inch. You won't be losing much at all going from 20" to 18.5"

I lost 25 fps when i chopped a .308 down to 18 from 22 inches. For me and that rifle it was worth it, I am still able to make hits at 1000 yards pretty reliably. I read on the forums that 25 fps is what i would lose and thats what happened.
 
Likes: wmfirefighter
Feb 15, 2017
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#11
When I started as an LE Sniper almost 20 years ago, I had a factory rifle with a 26” barrel that shot Hornady 168 gr. AMAX TAP at 2700 fps. About ten years ago, I switched to a custom rifle with a 20” Hart barrel. It shot the same ammo, unsuppressed, at 2650 fps. I just switched to an AI AX308 with an 18” Bartlein barrel about three months ago. It shoots the same ammo, unsuppressed, at 2550 fps. The barrel length certainly has an effect, but some barrels are just faster than others.

I like the 18” length for its handling qualities in close quarters, whether suppressed or unsuppressed. If you’re hand loading for comps, you can tailor your load to the longer barrel lengths, such as 24 or 26 inches, and likely get a little more velocity for improved performance at longer ranges. However, if you’re shooting suppressed, or shooting comps where the longer barrel lengths would be a disadvantage, I’d stick with 20 to 22 inches as the best compromise between handling and velocity, with 20 inches being my favorite length for a general purpose 308.
 
Likes: wmfirefighter

Jackalope

Sergeant of the Hide
Jun 8, 2017
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Flagstaff AZ
#14
I’d do 18” if you’re hunting with it. It’s just so much nicer to maneuver. DARPA did extensive research on .308 barrel length while developing the XM-3 and settled on 18.5”. When I cut my factory AAC-SD down to 18” it was still capable out to 1000 yards and none of the animals seemed to notice a difference.
 

bab029

Hammer Mechanic
May 16, 2011
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#15
Any perspective on going shorter, i.e. 16.5"? Thinking on this for a general fun gun and deer stand wackem stick. Full time suppressed.
 

OLD308

Sergeant of the Hide
Jun 8, 2018
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#18
I have 16-24” 308s in every conceivable variation. 18” with a 1/8 twist and 175 SMK accurate load is only 150 FPS (8208 xbr) off the accurate load for the 24”. I like the 18” over the 16” because the weight of the barrel balances the rifle better. It naturally points easier. Plus, 18” and a suppressor is a usuable length.
Velocity loss and barrel length is very powder dependent. When I use Benchmark powder the velocity difference between the 24 and 16 accurate load is 60 FPS. Just my experience.
 
Likes: bab029

Luvman

Full Member
Mar 17, 2003
594
22
18
Northern KY
#19
My AT came with a 20” barrel. I have plans for 18” 6.5CM and 16.25” 10 twist .308 barrel for it.

But I have no interest in any barrel over 22” for any caliber.

I say go 18”.