AR 15 barrel length question?

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

  1. lonewolf204

    lonewolf204 Active Member

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    Would a 20" barrel be more accurate then a 16"? Would it be worth the cost to change it? I'm talking about an Ar 15 in 5.56. I can not get these rifles to shoot as accurate as everybody says there's will shoot. Is the gas piston conversion worth the cost, will it help the accuracy?
  2. Tmergen24

    Tmergen24 New Member

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    Depens if your going from like a pencil to a bull barrel I'd say yes but if just increasing length I wouldn't do it and is it free floated
  3. Tmergen24

    Tmergen24 New Member

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    And with the gas piston it can be enough to affect barrel harmonics. It's minimal but at long range it may have an ill effect on accuracy
  4. 3/2 STA SS

    3/2 STA SS Active Member

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    Yes a 20" is more accurate. My M16A2 was a great weapon and it had a 20'' barrel. My M4 was good but the A2 was more accurate.
  5. GunHugger

    GunHugger Well-Known Member

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    No difference in accuracy between a 16" or a 20" of the same quality shooting the same ammo. Velocity would be slightly lower in the 16".

    Length does not effect accuracy. Barrel design, twist rate/bullet match, full floating the barrel or not, chrome lined or non chrome lined, ammo quality, 223, 5.56 or "other" chamber/bullet match, optics and the nut behind the trigger.

    Heavier barrels are not actually more accurate but they will not be effected by the barrel heating up as fast as a pencil barrel.

    You need to match your bullets to the barrels twist rate for best accuracy. Usually light bullets like a 40gr varmint bullet isn't a good idea in a fast twist rate such as a 1 in 7.

    A full floated AR barrel can shoot more accurately than one not free floated if shooting from a bench, bi-pod, using a sling or in any way that places pressure on the forearm or barrel.

    Chrome lined barrels can be accurate but usually they are not as accurate as non chrome lined. There are "target" barrels that are made to tighter tolerances, lapped to smooth the machining of the bore and whatever else the each manufacturer does to make them are the best choice for accuracy. Chrome lined barrels are made for blasting and for ease of cleaning but I have had a few that were very accurate.

    Good quality factory ammo or well made reloads will almost always shoot more accurately than military type ammo.

    In general a 223 or a Wylde chamber will shoot match bullets more accurately than a 5.56 chamber.
    If you want to read more on that here's a link to a short explanation of chambers in the AR.
    http://www.armalite.com/images/Tech%20Notes%5CTECH%20NOTE%2074%20%205.56%20vs%20223%20vs%20Wylde%20090817%20Rev%200.pdf

    With optics and accuracy, you get what you pay for. You will never shoot as accurate as your setup is capable of with cheap chinese $100 optics. I know some think they can, fine believe it if you want.

    Same goes for the mount.

    Sorry for the long post, nothing on TV, feel free to have a different opinion, these are mine.
  6. cpttango30

    cpttango30 Guest

    HUM Yes it does. The more time it spends in the barrel the better it will stabilize the bullet. Also a little extra length never hurt anything (That's what she said).

    My 20" shoots amazing groups.

    What kind of a barrel are you using? Chrome lined are not as accurate as unlined CRM or SS.
  7. GunHugger

    GunHugger Well-Known Member

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    Yes it does if you are talking extremes like a 6" and a 20". The topic here is a 16" and a 20". The bullet is just as stabilized out of the 16" as the 20".

    While we're on extremes would you think a 40" barrel would be more accurate than a 20"? Or might you think the shorter one would be more than enough to stabilize the bullet and the 40" would be overkill?

    I maintain that a 16' barrel is more than enough to properly stabilize the bullet.

    Your 20" shoots amazing groups...well I think it would be just as accurate if you chopped off 4".

    What barrel am I using? I have more than one. My most accurate barrel is the ArmaLite 20" AISI 416R Stainless Steel triple lapped heavy 1:8" twist on my M-15 National match rifle.

    I never said chrome lined barrels are more accurate.
  8. lonewolf204

    lonewolf204 Active Member

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    What's yawls opinion on the 223 Wylde?
  9. Tmergen24

    Tmergen24 New Member

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    Mines chambered in that and still shoots sub moa and it's nice to have the choice between the two calibers
  10. old semperfi

    old semperfi New Member

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    listen to gunhugger,he is right.try different bullet weights and shapes.no offense but let somebody else try.as far as length of barrel,if its long enough to stabilize projectile it can be six inches long and no effect on accuracy.i have a three inch 44mag model 29 smith that i have hit metal targets at 200 yards and it shoot no different than my six inch classic hunter.it is only the sight radius that may matter, old semperfi
  11. RunningOnMT

    RunningOnMT New Member

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    My totally uneducated guess is that a 20" barrel might be just a tad more accurate than a 16" due to increased velocity. Increased velocity = less bullet drop over longer ranges because the faster bullet hits the target sooner. But that difference in velocity and it's corresponding effect on the POI would be so slight it would likely be imperceptible.

    But I said that was a guess. For a real answer JLA is the man to tackle this question. He has spent many hours scientifically studying such things, and has corrected several misconceptions of mine regarding barrel/bullet mechanics.
  12. GunHugger

    GunHugger Well-Known Member

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    A little more velocity does not make it more accurate, it's just slightly faster.

    I wonder why almost all 22 target ammo is lower velocity.

    I tested the velocity of M193 ammo in a 16" and 20" AR with my chronograph and found an average of only 135 fps less out of the 16" barrel.

    I'm talking real world shooting here, not extreme circumstances where there may be a slight difference that most shooters would never notice.

    I'll step away from this discussion now and wait for those that know about this stuff. :)
  13. zkovach

    zkovach Active Member

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    Take these suggestions above.

    My first lr308 was awful accuracy wise however I changed out the trigger and it's been great since! The ar-15s I have shot after that the trigger has been fine. Id suggest looking at ammo first then the trigger. Definately have someone else shoot it first as suggested above. Do these things one step at a time.
  14. lonewolf204

    lonewolf204 Active Member

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    I have a 3 pound Timney trigger! I have shot a lot of different bullet weights from several manufacturers and still can't get sub Moa! I have shot bolt guns for years at sub Moa. I might be expecting to much from an AR!
    Last edited: Aug 13, 2012
  15. RunningOnMT

    RunningOnMT New Member

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    You probably are. A semi auto vs bolt action is not a a fair comparison.
  16. aa1911

    aa1911 Active Member

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    I'm in agreeance with Gunhugger. that small difference will not necessarily equal greater accuracy all things being equal. Matching bullet length to barrel twist is extremely important for accuracy and stability, overal max performance.

    .22 LR for example, after about 17", any extra barrel length is completely unnecessary; hence the 'bloop tube' on small bore target rifles. A standard velocity round gains nothing past that 17" (approx) mark but you do benefit from a longer sight radius.

    16" is a fair length for very good accuracy IMO
  17. lonewolf204

    lonewolf204 Active Member

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    What kind of groups should I expect @ 100 yards?
  18. tcox4freedom

    tcox4freedom Well-Known Member Supporting Member

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    I'm subscribing & hope this thread goes for awhile. My wife just bought her 1st AR and I'm hoping to get one soon. So far, I'm liking what gunhugger has to say.

    Personally, I would 1st determine what the primary purpose of the AR will be. For us, it's home defense. We live in the country and may also be killing a few yotes. But, so far I think the 16" S&W 15 Sport is filling the ticket for our needs.

    I've only shot it twice. But, can get 2" groups at 50yds & 4" groupings at 100yds just using the stock iron sites or a cheap Barska 1x RD sight. To me, this is plenty good for HD & killing varmints out here in the country.

    Conversely, I have a cousin that's not happy if his groups aren't smaller than a quarter @ 100yds. (Me, I'm happy with combat accurate.)
    -
    Last edited: Aug 13, 2012
  19. aa1911

    aa1911 Active Member

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    if 4" is plenty good at 100, you could easily use a 6" barrel! my 10.5 shorty did some good work out to 400+ meters with no problem with accuracy or velocity. sniper gun? nope. but it will print an easy 1.5 MOA with military green tip, probably less if human error was removed.

    16" is plenty of length to achieve 1 MOA IMO, good velocity also.
  20. polishshooter

    polishshooter Active Member

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    For what it is worth, my Rock River 16" HB chrome lined 5.56 chambered 1/9" twist standard long length gas tube NON free floated WILL do 1" at 100 with Black Hills 50 grain "factory reloads" (or my 50 gr Dogtown reloads I worked up for it) IF I have the Bushnell 3x9 on it....and with my 54 year old eyes...which is not BAD for what was the FBI "Entry Weapon" at the time I bought it....LOL:eek::cool:


    (AND oh yeah I have the FANTASTIC 2 stage "match" trigger that comes STANDARD with the Rocks....$125-$150 or so if you want to add it to any other AR:D;) And it is WORTH it....

    With the cheap Federal XM 193s or PMC hardball that I shoot the most and the Dominator (peep) rear sight on it with the same eyes I am happy if I get 2-3" at 100...from a SOLID rest..;)

    I remember the first time I shot it from the range at 100, with the peep sight and XM193s, just from my shooting bag as a rest...with my son shooting my Yugo /59 unmodified SKS with it's "gate latch" trigger next to me with elCheapo Wolf steel cased x39 ammo from a wobbly 2x4 rest next to me...and I was getting bigger groups than HE was...about 7-8"!!!!:eek

    But with the scope and the Black Hills I shot prairie dogs out to 175 with it for two years, but yes I got "snobbish" after shooting my .30-.40" groups at 100 and 2" groups at 400 yds with my M77 VR Swift and this year the AR stayed in the case....

    That being said, my next upper is already being planned...18" SS heavy barrel (maybe fluted?) free floated with a .223 Wylde chamber with my same lower I will EXPECT to shoot almost as well as the Swift if I put a decent scope on it. (I am thinking of maybe a Nikon AR 4-12x variable....)

    MANY guys use ARs shooting 'dogs and targets and they can be and are JUST as accurate as any bolt gun..if they are set up for it...


    The only reason I may not build up my "Varmint" AR is simply that I like to neck size only (the ONLY accuracy advantage a bolt gun has over a "modern" semi auto now) AND I don't like crawling around on the prairie among the cacti and rattlesnakes and bubonic plague carrying FLEAS looking for my BRASS:eek::rolleyes::cool::p:p
    Last edited: Aug 14, 2012
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