AR 15 barrel length question?

Discussion in 'Large-Bore/Small-Bore Rifle/Shotgun' started by lonewolf204, Aug 12, 2012.

  1. aa1911

    aa1911 Active Member

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    In my hi-power service rifle days, 16 was standard (and the reg) for AR's and were plenty capable and very accurate, even at 1000yd matches. No 'external' mods were permitted, probably the same still. Colt with Douglas SS match barrels were pretty popular then. I was an M14 guy so didn't mess around with mouse guns very much until the military.

    Some of the space gun guys had bloop tubes so I have no idea what their true barrel lengths were.
  2. Albtraum

    Albtraum Member

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    Where did you get 17" inches from? The writer of Gunblast did a little testing with a Ruger 10/22 Carbine, and a Ruger Charger (10" pistol with 10/22 action) using high velocity Federal hollow point, he chrono'd "1203 feet-per-second (fps) from the sixteen inch barrel, but still averaged 1163.9 fps from the ten inch Charger barrel." Barely 44 fps from a 10" barrel to 16". Chronos from even smaller handguns still exceed 1000 fps, just shy of what a rifle barrel would produce.

    I think what makes a longer barrelled gun "more accurate" is that it is easier to hold steady and hit your target. Like a snub nose revolver vs. a full size service pistol, or a small lightweight carbine vs. a heavy rifle. They might be equal when on a vice, or bench, but when shooting off hand you'll see the merits of the larger weapons. If barrel length had no effect on performance, what was the reason for the big bulky near-30" barrel muskets, Mosins, and M1 Garands? While there may be subtle differences in accuracy between a 16", 20", or even a 24" bull barrel, I think you know which would be the easiest and most predictable to hit your mark.
    Last edited: Aug 14, 2012
  3. aa1911

    aa1911 Active Member

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    Albtraum, you're on track with me in general but I should have clarified a bit more, I'm talking from the target rifle stance:

    17" was the well accepted number thrown around the smallbore target shooting arena in my younger days, I have no facts to back that up. However, even a 100 fps difference means there is a difference. Like you said and others here, it may be a small difference so technically.... but 17 was a technical reference to where the bullet stopped gaining performance in both accuracy and velocity.

    Velocity was not the only factor for that 17" theory; it was all things related to smallbore target shooting. velocity was one but also bullet stability. And I should have clarified standard velocity ammo for this as well, no target shooter is using Hi-vel stuff, not sure how much difference there is there as far as max barrel length.

    Black powder guns generally need more barrel for the relatively slow burning 2 or 3F powder to develop good velocities. I've no personal experience with the 'modern' BP stuff.

    but you are correct in saying that extra barrel length will also increase accuracy because of weight/balance. but only when you are talking position shooting; put it on a bench and that factor is gone completely, just as you stated. And remember, we're assuming the shooter is a 400-40x capable (potentially anyway) so I'm talking only about the gun's capability, not the shooter or his technique.

    Once you reach a certain point, (say 14-16" in the AR), we're talking a much bigger emphasis on length for the job vs. extra accuracy or velocity for that 2-4" difference. If you're clearing rooms, stay short; if you're needing a long range performer, stay on the longer side to maximize performance. Just realize it is often a small difference.
  4. lonewolf204

    lonewolf204 Active Member

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    In a 1-9 twist what bullet weight are you getting the best groups with? I have been shooting 55, 60, 62, 64, and 69 grain bullets and a 3" group is the best I can get.
  5. GunHugger

    GunHugger Well-Known Member

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    What 16" barrel are you talking about?

    Chrome lined?

    A 5.56, 1.9 twist...that about right.

    If you want tighter groups, a Wylde or 223 chamber shooting good hand loads or factory 223 ammo like Hornady will do much better with any of the bullets weights you mentioned.
  6. polishshooter

    polishshooter Active Member

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    The only ammo that I have shot 1 inch groups with out of my chrome lined 16" HB 1-9" Rock River is Black Hills 52gr Match Hollow Points.

    I get close with my 50 gr Dogtown (Nosler) reloads.

    Standard 55 grain fmj Federal or any other I am lucky to get 2 " groups with.

    Any heavier bullets I seem to get from 2-3" groups.


    I don't know if this is typical or not, but that is what I get. And oh yeah from a BENCH with sandbags, the whole nine yards.

    Just leaning the rifle against anything gets me twice as much, offhand for me is really about the same as any other rifle at 100, custom or surplus, heck, my smoothbore SLUG gun for that matter but that probably has more to do with the fact I SUCK at "Awfulhand" than the rifle;):cool::cool:
  7. lonewolf204

    lonewolf204 Active Member

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    I am attemping all this from a bench with sand bags and a leupold scope. I could be using to heavy of a bullet weight for the 1&9 twist. I will try some lighter ones.
  8. lonewolf204

    lonewolf204 Active Member

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    Update: I added a free float fore end and tightened the play between the upper and lower receivers. I shot 1" groups today with 3 different brands of ammo and the same 16" barrel I was wanting to replace. I think I can live with it know.
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