AR 15 barrel length question?

[lonewolf204]

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?

[Tmergen24]

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

[Tmergen24]

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

[3/2 STA SS]

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.

[GunHugger]

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%...%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.

[cpttango30]

Length does not effect accuracy.

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.

[GunHugger]

Originally Posted by cpttango30

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.

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.

[lonewolf204]

What's yawls opinion on the 223 Wylde?

[Tmergen24]

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

[old semperfi]

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

[RunningOnMT]

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.

[GunHugger]

Originally Posted by RunningOnMT

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.

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.

[zkovach]

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.

[lonewolf204]

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!

[RunningOnMT]

Originally Posted by lonewolf204

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 Mao! I have shot bolt guns for years at sub Mao. I might be expecting to much from an AR!

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

[aa1911]

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

[lonewolf204]

What kind of groups should I expect @ 100 yards?

[tcox4freedom]

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.)
-

[aa1911]

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.

[polishshooter]

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


(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 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

[aa1911]

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.

[Albtraum]

Originally Posted by aa1911

.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.

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.

[aa1911]

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.

[lonewolf204]

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.

[GunHugger]

Originally Posted by lonewolf204

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.

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.