What length barrel for all purpose AR 308 upper?

[aheadofthecurve]

I'm considering to get a 308 upper that I'd like to be able to shoot heavy metal/optics with, as well as doing some longer range relatively precise shooting (I'm thinking out to 900 yd or so).

Would an 18" be ok, or would I benefit alot from a 20 or 22? How much velocity would I lose with an 18? Any other considerations?

BTW I'm thinking JP at the moment.

[The Surgeon]

for every (1 inch) you gain you will also gain about 50 fps. The same rule applies to every inch you cut off.

[bigbrowndog]

I shot an 18" in a long range match and did very well against others that had longer barrels, barrel length really doesn't matter except in velocity, and if you know that, and your ballistic data then it matters not!!! what your barrel length is. I shot 155 hornady's at 2600fps, the gun gave me consistent moa accuracy out to 600yds. I also shot HM multigun with it scoped with an ACOG and using Irons, it does well at that also, however you give up some sight radius going with irons mounted out on the muzzle over a 20" barrel. You really do not lose anything in handling going with a 20" barrel over the 18" and you gain some velocity. My loads chrono 2690 in the 20" gun and 2600 in the 18" gun. I would go with 20" for an all-purpose gun, which is what i plan to do when it becomes rebuild time.

Trapr

[Religious Shooter]

If I had to have one I would get a 20". Just because.

[landshark45]

I went with a 20in. If your really wanting to push the range 600-900yds the extra length will keep the bullet super sonic. I shot my 20in in 30deg weather one xmas and around 850 yds or so I believe my rounds went subsonic and I couldn't hit the 900yd target. My 26in with the same rds 168gr Sierras had no problem out to 1000yds. The barrel length seems to matter for certain rounds stability when crossing the transonic barrier.

[Graham Smith]

Accuracy at distance depends on the distance, projectile, and wind. Once the bullet goes transonic, then the bullet is more subject to wind deflection. If you are shooting under 700yds, then an 18" barrel should not pose any problems, but if you are going much beyond that then you want to keep it over 1340fps as long as possible. A 20" barrel in a bolt gun is turning out to be a good compromise between length and portability. I expect the same would be true of a semi-auto.

[Mbauer67]

I went with a 20in. If your really wanting to push the range 600-900yds the extra length will keep the bullet super sonic. I shot my 20in in 30deg weather one xmas and around 850 yds or so I believe my rounds went subsonic and I couldn't hit the 900yd target. My 26in with the same rds 168gr Sierras had no problem out to 1000yds. The barrel length seems to matter for certain rounds stability when crossing the transonic barrier.

A 20" barrel is a good compromise, Ben (the guy who shot with us a bakersfield) has a 20" M1A and it does not feel any bigger than a 18" 223 when moving in and around things. Im my opinion you want to get an much FPS as possible when shooting the longer distances. I would probably go with a 20.5" barrel, just so mine is bigger than Gordon's.

[landshark45]

It seems that 20in is the most practical length in the 308 AR platform. Based on the above responses.

[Tom Freeman]

I have a 25 inch 260 that does not feel terribly long. I am used to a 28 inch AIAW however.

But when I put a suppressor on it, it does feel a bit muzzle heavy.

20 or 22 would be my choice. 22 if you wont/cant run a can.

[CraigS.]

I would start with a medium contour 20" barrel, because you can always make it shorter.

or you can build a 2nd upper thats what I did .

I have a 18" heavy contour and a 22" medium contour both weigh the same but the balance

is different.

[Csiedmond1]

I'd say 20", that's what I'm building for the same kinda things you are!