Which length of Bull barrel for an AR?


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nolyaw
March 25, 2008, 08:17 AM
I want an AR with a bull barrel for long range target shooting, in .223. Which would inherently provide the best chance for accuracy, a 16" or a 20"? Is there that big of a difference?

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ocabj
March 25, 2008, 09:05 AM
20" for higher muzzle velocity and longer sight radius.

1:8" twist or faster for heavy bullets.

Ridgerunner665
March 25, 2008, 09:09 AM
18 inches will get you all the velocity you can get from a 223 as long as you load the rounds with the correct powder for the bullet weight you are shooting. Most are 20 inches, some are 24...and 24 is definately a waste (except from a sight radius standpoint...and if you use a scope, that point is moot).

Seafarer12
March 25, 2008, 09:28 AM
24 isn't a waste. If he is reloading and wants to wring everybit out of that 223 a 24 in is the way to go. that said they are long and heavy. 20 inch is a happy medium. I wouldn't even consider a 16 for a target gun.

As far as sight radius its a moot point bull barrles very seldom have open sights on them.

Ridgerunner665
March 25, 2008, 10:09 AM
I can get just as many FPS from an 18 or 20 inch as you can from a 24....just with different powders.

How many fps can you get from a 24 inch with a 60 grain bullet???

I can get over 3,000 fps from a 16 inch barrel and a 60 grain Hornady V-MAX bullet...the 223 does not have the case capacity for barrels that long...but people want them, so companies make them.

Bendutro
March 25, 2008, 11:23 AM
Is the gas block in the same place on 18, 20, 24 inch barrels?

What does that pressure drop do to the MV?

Ridgerunner665
March 25, 2008, 12:21 PM
Yes they all have rifle length gas systems.

The pressure drop occurs too late to have any noticeable effect.

Bendutro
March 25, 2008, 01:49 PM
Ridgerunner, you must be using faster powders to get 3000fps out of a 16" with a 60gr bullet. Are your cases showing any signs of high pressure fatigue?

I wanted a varmint-specific AR, so I bought the Stag model 6. It has a 24" bull barrel but after I shoot that a while I wouldn't be averse to chopping a few inches off and rechambering for AI.

nolyaw
March 25, 2008, 05:54 PM
So a 20" would be best, over a 16"?

Bendutro
March 25, 2008, 06:38 PM
Buy what you want, they all shoot.

http://www.geocities.com/graymist44/Rem223.html
Varmint Loads - 223 Remington

Ridgerunner665
March 25, 2008, 08:06 PM
AA2230 was the powder used for that load...one thing I should mention is that my gun has a 5.56 NATO chamber...the 223 Remington chambered guns can only be loaded to 50,000 psi..some say 52,000, while the NATO version can be loaded to 60,000 psi.

With plain CCI small rifle primers...that load will flatten them just a little...but with CCI 41 primers, which are made just for 5.56x45 mm, they are just fine. Of course case life is shorter, I load them 2 maybe 3 times.

If you're havving a gun built or buying one...be sure to get either a 223 Wylde chamber or a 5.56x45 chamber...not a 223 Rem. chamber.

And...yes a 20 inch barrel is PLENTY long enough for a varmint or target AR...18 would do just as good.

Ridgerunner665
March 25, 2008, 08:24 PM
Here is a link to a thread over on 1911auto forum...posts #25 and #26 are especially interesting
http://1911auto.org/forum/showthread.php?t=1604

My learning experience of reloading for a 5.56x45 mm is documented online...I got tired of settling for 223 Rem loads... 5.56x45 loading info is scarce...but if you look hard enough...its there.

BTW...Feel free to join the 1911auto forum while you're over there...its only been there since this past December, but its growing fast... its a nice place, with a crew of really nice guys running it.

dscottw88
March 25, 2008, 08:34 PM
I'd go with an 18, I think 18s are under appreciated. Troops are beginning to use 18 inch DM rifles with 70-grain rounds successfully in the sand box.

Ridgerunner665
March 25, 2008, 08:45 PM
The military spent a lot of time and money to figure out that 18 inches was the optimal barrel length for an m16...and that was over 30 years ago. Due to the advancements in powders...its even more true today than it was 30 years ago.

taliv
March 25, 2008, 11:21 PM
ridgerunner, since this isn't in the reloading thread, where there are warnings about posting load data above maximums, i feel obliged to say i think you need to be careful with this advice.

accurate's max published load using a 24" barrel is 3024 fps using 2230 and the 60g hornady. Given that you lose ~100 fps going from a 20" to a 16" barrel and probably another 100 fps going from 24" to 20", I can only assume you're loading well above maximum.

I know there are those here who like to push limits, but telling folks they can use load data that puts you 200 fps over the published maximum is treading close to irresponsible. especially after reporting pressure signs in your own loads.

as you may know, many mfgs mislabel their chambers/barrels. it's generally unwise to arbitrarily bump your load up because you think one chamber can handle 10k more PSI than another. and that assumes you have the equipment to measure pressure.

rbernie
March 25, 2008, 11:43 PM
I want an AR with a bull barrel for long range target shooting, in .223. Which would inherently provide the best chance for accuracy, a 16" or a 20"? Is there that big of a difference?My 75gr Hornady OTM loads clock out at about 150fps-175fps slower in my 1:9 16" Armalite barrel (5.56 chamber) than they do in my 1:8 20" Shaw barrels (with a 223 chamber).

Also - always keep in mind that bolt guns and semiautos are different beasts. Anyone shooting an AR with a range of handloads knows that port pressure and dwell time differences between loads can cause significant functional stresses and anomolies. In fact, the Sierra loadbook has a completely separate section for 223 in boltguns vs semiautos, for this very reason. You can play with loads in a bolt-gun in ways that are simply Not Good JuJu for an AR15.

I prefer to get velocity thru barrel length rather than abnormally high chamber pressures. It's easier on the equipment, and for a range/target rifle I don't mind a little extra weight due to the longer tube.

Having said that - shorter barrels are sometimes actually more accurate (they just make a little less velocity).

If you're looking for max range, I'd definitely go with a 20". If you're looking for the ultimate accuracy within, say, 200-300 yards then the 16" may give you a minor increase in accuracy at the expense of some trajectory drop downrange.

Ridgerunner665
March 25, 2008, 11:52 PM
I measure pressure by measuring the case heads for expansion...the warnings are there...I did say that my gun DOES have a 5.56 chamber...these loads are above max for a 223 Remington...but they are right on for a 5.56x45.

You haven't listened to what I've been saying...you do not lose 100 fps by going to from a 16" to a 20"...neither do you lose another 100 fps by going from a 20" to a 24" when your gun is chambered in 5.56x45...I'm not talking about a 223 here...223 load data is useless for any AR chambered for a 5.56x45...except maybe for plinking ammo or to use as a start charge for a 5.56x45.

Yes some makers may not mark their barrels correctly...its only a few $$$ for a smith to tell you for sure...thats up to the owner (and only then if they purchase a rifle from somebody who would mark their barrels wrong).

The only reason I had any pressure signs with my loads was because I used CCI 300 primers...there were no flat primers when I used the CCI 41 primers.

I don't think my chamber can handle 10k more PSI...I know it can, because of the company that built my AR and what they built it for.

I see your point...but a person should have the common sense to either know what they bought...or at least be able to find out, its not that hard to do.

Ridgerunner665
March 25, 2008, 11:55 PM
rbernie...those heavy bullets are another monster...they do need the extra barrel length (and slower powders) to get going.

Ridgerunner665
March 26, 2008, 12:11 AM
I'm going to say one more thing on this thread then I'll shut up since it seems that hard earned knowledge isn't welcome here.

Whats the point in having a 5.56x45...if you're going to load it with 223 ammo.

huckster
March 26, 2008, 12:13 AM
I use an AR with a 20 inch bull barrel for NRA Highpower competition. It does well out to 600 yrds with iron sights.

I've tried an 18 inch and it didn't perform nearly as well. I haven't tried anything longer.

I've never seen an 18 incher on the line at camp perry.

Art Eatman
March 26, 2008, 12:58 AM
Ridgerunner, don't take this as any sort of personal slam:

This is the Internet. Nobody can tell if any one person is correct or not without some lengthy track record of posts and feedback over time.

The possibilities of Ridgerunner's system may work. We have no way of knowing if he's one more shot away from a damaged rifle. I'm not at all predicting; I'm saying we don't know as fact.

If anybody wishes to follow his suggestions, fine. However, as with any load development, start low and buildup slow. Do NOT jump in and immediately follow the notion of, "Well, he said he loaded it like this, so I can do the same."

I note in passing that the strength in shear of the lugs of a bolt-action rifle is greater than of the AR-15; more cross-sectional area. For a push-feed action, there is no benefit to 5.56 over .223.

I will take exception to the comments about barrel lengths and velocity loss. For there not to be a loss from 24" to 20" or from 20" down to 16", it would be the first time in my 58 years of messing with centerfire rifles that this has occurred.

There have been numerous experiments where barrels were cut back an inch at a time and a chronograph was used. Shorter = slower, invariably. And a centerfire .22 is a centerfire .22, no matter how you meddle around with the loadings.

jpwilly
March 26, 2008, 01:06 AM
I had the same question a few years ago and got the 20". More velocity and less muzzle blast. Also shoots very small groups!

http://i124.photobucket.com/albums/p38/jpwilly/ARBULL20-1-1.jpg

http://i124.photobucket.com/albums/p38/jpwilly/5shots100yrdsFAE.jpg

http://i124.photobucket.com/albums/p38/jpwilly/3shotsat100yrdshalfFAE.jpg

http://i124.photobucket.com/albums/p38/jpwilly/3shotsat100yrdsFAE.jpg

Ridgerunner665
March 26, 2008, 01:42 AM
Art...Thank You

I dont take it as a slam.
I should clarify something I don't think I have made clear though....with the exact same load, you will lose fps in a shorter barrel...but most of the time, by matching your powder burn rate to your barrel length and bullet weight...you can match the velocity of the longer barrel. The real fast powders with heavier bullets in long barrels for example, the pressure drops and the bullet starts slowing down before it even exits the barrel. This is especially true when talking about cartridges with a small case capacity.

I get in trouble every time I start talking about reloading.

And just for the record...I didn't post any loads on this thread...the loads on the other thread are full of red letter warnings.

Conqueror
March 26, 2008, 11:50 AM
Ridgerunner - I think you only got jumped on here because you only focused on velocity and not bullet weight. You can get 3k with a 60gr V-max out of 16, but I can easily get 3k with a 75gr A-max in my 26" white oak barrel. And when varminting is the game, a heavier bullet will obviously let you reach out a bit farther with less drift.

eldon519
March 26, 2008, 09:34 PM
Ridgerunner, I am curious where you have found your information about bullets slowing in the barrel when using faster powders. This contradicts most everything I have ever seen regarding modern bottleneck rifle cartridges.

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