I just got into AR shooting and I'm a tack driver. I developed a 5.56 NATO load that works well at 100 yards with the stock barrel of a S&W M&P 15 but I want to go out to 600 yards so I'm looking at varmint barrels. http://www.model1sales.com/ind...play&category_id=264 Now on an AR forum, I'm told your best accuracy is with shorter barrels which I find hard to believe while others say going all the way to 24" is too far and you will lose accuracy and speed. There are so many conflicting stories, I thought I'd bring it to the experts; what's the real story. My current load is with a 52 grain boat tail bullet at about 2900 fps.

Both could bee right a long barrel is heavy and give a stabile rifle. A short barrel has less traveltime for the bullet, while parts are moving in the action.

This is my reply on the AR forum:

I'm confused, if a 5" barrel handgun is much more accurate than a snub nose and a rifle much more accurate at longer distances than a handgun, how is it that AR's are somewhat opposite? This confusion led me to the Savage web site as they are known for producing very accurate rifles. In their "Bench Rest" category, the Model 12 F/TR in .223 Rem has a 30" barrel. Why is that an accurate gun and an AR platform with a 24" barrel isn't? Seems to me that what platform strikes the primer is inconsequential when it comes to a bullet traveling down a barrel, except of course things like bedding.

Any comments?

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Weight isn't a factor as I am using this for bench rest shooting at 600 yards.

I'm not trying to be a smartly, I think I may have answered my own question.

i believe the bit about short barrels being more accurate comes from many years back. the benchrest crowd has weight limits on classes of rifles. to have a long heavy barrel went over the weight limit, so they shortened up the barrel, got into the limits and since the heavy barrel vibrates a bit less, got better groups, maybe not because of the short barrel, but because of the diameter

That makes sense.

The accuracy of a rifle is not necessarily dependent on the barrel length. There are many factors at play. Here are just a few to consider.

When using iron sights, including peep and target types, the distance between the front sight and the rear sight determines your sighting plane. With a longer barrel you can have a longer sighting plane. Generally, the longer the sighting plane, the more precisely the sights and target can be aligned, and the more accurately the shooter can aim and shoot his rifle.

Barrel harmonics will greatly effect accuracy. When the bullet travels down the bore of a rifle it causes the barrel to whip and twist as it squeezes along the rifling. You cannot see this happening because it is very slight and very rapid but it happens nonetheless. Wherever the muzzle ends up in this ballet is where the bullet will be released to go down range. Shot to shot variations occur because there are always differences in the true bullet weight, the exact powder amount, how tighly the bullet is being held in that particular case, etc. These variations are part of the reason you can fire twenty rounds and record twenty slightly different velocities. The result is that, as each bullet leaves the muzzle, the exact position of the muzzle will vary slightly. Accuracy is all about doing everything the same from shot to shot. A long, thin barrel will whip and twist more than a shorter and thicker barrel. So, regarding barrel harmonics, you can generally say that the thicker the barrel and the shorter the barrel (within reason) the more consistently the bullets will leave the muzzle and result in better accuracy.

How far is the target? As bullets slow down on their way to the target they can become unstable as they approach the speed of sound and become transonic. Severe instability can occur at transonic speeds. Shock waves move through the air at the speed of sound. When a bullet moves faster than the speed of sound it moves ahead of a very large shock wave. During transonic flight, the bullet slows down and must allow the shock wave to pass over it as it moves to the front of the bullet. This causes instability because air is moving faster than sound over one part of the bullet while moving slower than sound over the other part. Therefore, it is critical to insure that your bullets can remain well above the speed of sound all the way to the target. Many cartridges, including the 5.56mm, must use a long barrel to achieve an initial velocity great enough to ensure the bullet will remain supersonic at very long ranges. So, for long range shooting, a short barrel may not create enough initial velocity. In this situation, the longer barrel will generally result in better accuracy. And that 30" Savage barrel is probably generating enough velocity for shooting well beyond 600 yards.

What position will you be shooting from, how will you be holding the rifle, how long will you be holding it, and will there be accessories attached to it? Barrel length and weight effect your ability to hold the rifle steady and for repeated shots. Sometimes shorter barrels are better for a stable shooting position and sometimes longer barrels are. It all depends on the rifle, how it ballances, how it fits into you and your shooting position, and how heavy it is. I used to qualify with the 20" barreled M16. When it was replaced by the 14.5" barreled M4 I saw my qualification scores go up. I believe it was because the shorter, lighter rifle was easier to maintain a good shooting position with for the kind of shooting I was doing . I also competed with the M16. But the M4 would not have been as accurate as the M16 for those competions because of the kind of shooting I did in the matches.

So, as you can see, there is much to support both an argument for longer barrels and for shorter barrels to be more accurate.

Since you want to shoot beyond 600 yards you will need to be careful you do not end up with bullets hitting the target at transonic or subsonic velocities. Your 52 grain bullet would probably need to be going over 3200 fps to do that. To get it there would likely require a hot load AND a longer barrel. But, longer, heavier bullets tend to retain their momentum better and are better suited for shooting at long range.

For your specific requirements for 600 yard shooting with an AR you are much better off with a longer barrel and shooting heavier bullets.

Bullet weight will be my first investigation; 52 GR isn't a lot of mass. I'll see what my current load does, heat it up then heavier bullets.

Just got off the phone with E. R. Shaw (maker of that barrel) he says the 24" is a fine choice for long distance .223. He said at Camp Perry they're shooting 800 yards with a .223 with excellent results, that makes my heart skip a beat in anticipation. As I expected I should go to a heavier bullet so it's off to load charts to see if I'll be heavy enough for a 1 in 9 or 1 in 8 twist.

Berger recommends the 1:9" for their 70gr and 73gr bullets, 1:8: for their 75gr to 82gr bullets, and 1:7 for their 90gr bullet.

Nosler says 1:9" for their 69gr HPBT, and 1:8" for their 77gr and 80gr HPBT

quote:

Originally posted by wboggs:
at Camp Perry they're shooting 800 yards with a .223 with excellent results.

And NONE of them are using short barrels.

Maybe some of the female posters should weigh in on this length discussion.

Random thoughts, baised on my personal actual shooting.

A 10 to 11 inch barrel is plenty accurate to make head shots at 100 yards, body shots to 300 yards.

14 to 16" barrels are deadly accurate to 400 and 500 yards.

I have shot 20" barrels quite a bit in Service Rifle competitions to 600 yards with excellent results.

If I was building a 223/5.56 rifle to shoot past 600 yards, I would use a 24 to 26" barrel and a 1 in 7 twist.

I prefer the longer barrels, and heavier barrels for that matter, like 26 inch in bolt rifles and in 223 bolt rifles. They generally produce a little more velocity which is helpful and the heavier barrels can shoot more without as much heat.

Beings I shoot the 69 grain bullets in a variety of rifles I prefer the 1 in 8 or the 1 in 7.7 twists. With the 69 grain BT Sierra MK about 500 yards is the accuracy limit. With the 77 grain bullets and more you can go more but as was said above you will need the faster twist barrels. I don't have any experience with the 77 and 80 grain bullets to offer. Interestingly a couple of my 1 in 8s shoot the 40 grain speed burners very well at 100 and 200 yards too.

In an AR platform rifle, and when using a longer barrel you may want to give some thought to the barrel profile. Again as I prefer the heavier barrels and longer barrels, it could put some stresses on the lighter weight unsupported barrel area of the receiver of the AR. I have not yet had the barrel fluted under the hand guards which can allow the longer and heavier barrel and still shave of about a pound. But I have looked at ordering just that from Compass Lake when I need another barrel. A lot of the varmint and longer range barrels are 24 inch for AR rifles.

Another thing to consider is balance and how you are going to shoot it and use the rifle.

If you are walking a lot then obviously it might not be the best setup.

If you are shooting prone and using a bipod then lots of weight out front can be an issue for some in some cases. My preference is to balance that out with a heavier and more lengthy stock like the Magpul PRS stock.

quote:

Originally posted by Rub Line:

quote:

Originally posted by wboggs:
at Camp Perry they're shooting 800 yards with a .223 with excellent results.

And NONE of them are using short barrels.

Probably not since longer barrel = bullet stability.

quote:

Originally posted by Grenadier:
Berger recommends the 1:9" for their 70gr and 73gr bullets, 1:8: for their 75gr to 82gr bullets, and 1:7 for their 90gr bullet.

Nosler says 1:9" for their 69gr HPBT, and 1:8" for their 77gr and 80gr HPBT

Sierra makes the same recommendation and 77 grain is the bullet I bought.

TWIST RATE = Stability
BARREL LENGTH = Velocity
BALLISTIC COEFFICIENT = Velocity sustainability
BULLET WEIGHT = Wind resistance

The higher the bullet weight, the higher the BC and the higher the wind resistance(inertial resistance to deflection.

Given a specific load, bullet and velocity with the correct twist rate, the longer the barrel the higher the velocity, the higher the velo/BC/weight, the lesser the drop and wind deflection.

Within various ranges, MANY combinations give match wining results...this game is like golf/bowling/pool...ain'no two shots/rifles/shooters the same.

Not to stir the pot, the shorter barrels of the past was to fit certain criteria as butchloc suggested...rules is rules...

One thing not mentioned so far - for the AR platform - is that a long, heavy barrel will stress the front of the receiver if free-floated. The aluminum receiver is not meant to carry the weight of a long heavy barrel without deflection, and this will effect accuracy especially as the barrel heats up. This is not an issue with a bolt gun since the free-floated barrel can be supported ahead of the receiver with a short pad of epoxy, not possible with the AR.

A compromise of length and weight is required, the heaviest barrel is not always the best on the mouse guns.


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quote:

Originally posted by TX Nimrod:
One thing not mentioned so far - for the AR platform - is that a long, heavy barrel will stress the front of the receiver if free-floated. The aluminum receiver is not meant to carry the weight of a long heavy barrel without deflection, and this will effect accuracy especially as the barrel heats up. This is not an issue with a bolt gun since the free-floated barrel can be supported ahead of the receiver with a short pad of epoxy, not possible with the AR.

A compromise of length and weight is required, the heaviest barrel is not always the best on the mouse guns.


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Isn't the front of the gun supported by the hand of the shooter?

I talked to E. R haw at great length about my desire to make a tack drive gun and I'd think if the barrel would damage the gun, they would have mentioned that. I have to say that premise sounds ridiculous.

quote:

Originally posted by wboggs:

quote:

Originally posted by TX Nimrod:
One thing not mentioned so far - for the AR platform - is that a long, heavy barrel will stress the front of the receiver if free-floated. The aluminum receiver is not meant to carry the weight of a long heavy barrel without deflection, and this will effect accuracy especially as the barrel heats up. This is not an issue with a bolt gun since the free-floated barrel can be supported ahead of the receiver with a short pad of epoxy, not possible with the AR.

A compromise of length and weight is required, the heaviest barrel is not always the best on the mouse guns.


.

Isn't the front of the gun supported by the hand of the shooter? The hand supports the hand guard but the hand guard does not support the barrel because it's free floating.

I talked to E. R haw at great length about my desire to make a tack drive gun and I'd think if the barrel would damage the gun, they would have mentioned that. I have to say that premise sounds ridiculous.

Since most AR manufacturers offer heavy barrel varmint variants of at least 24", I would not lose any sleep over it.

quote:

Originally posted by Rub Line:

quote:

Originally posted by wboggs:

quote:

Originally posted by TX Nimrod:
One thing not mentioned so far - for the AR platform - is that a long, heavy barrel will stress the front of the receiver if free-floated. The aluminum receiver is not meant to carry the weight of a long heavy barrel without deflection, and this will effect accuracy especially as the barrel heats up. This is not an issue with a bolt gun since the free-floated barrel can be supported ahead of the receiver with a short pad of epoxy, not possible with the AR.

A compromise of length and weight is required, the heaviest barrel is not always the best on the mouse guns.


.

Isn't the front of the gun supported by the hand of the shooter? The hand supports the hand guard but the hand guard does not support the barrel because it's free floating.

I talked to E. R haw at great length about my desire to make a tack drive gun and I'd think if the barrel would damage the gun, they would have mentioned that. I have to say that premise sounds ridiculous.

Since most AR manufacturers offer heavy barrel varmint variants of at least 24", I would not lose any sleep over it.

I hate to say it but that's the most ridiculous thing I've heard yet on the subject.

So what you're saying is if I pick the gun up by the for end stock, the barrel will fall on the floor? When I look at my gun the front of the front stock is attached to a solidly mounted receiver that it slips into that surrounds the barrel (hence attached to the barrel) therefore the front barrel is supported by the left hand of a right handed shooter, period. Secondly the notion that a bull barrel will destroy the accuracy of the gun because it will stress the lower end of the gun from its weight is further crazy unless you're shooting it one handed like a handgun. The barrel is a self contained unit that does all that's required to shoot a bullet except hit the firing pin, that's the only function the lower had in the firing of a projectile except you're holding it there and pulling the trigger. If you could strike the trigger without the lower, it would be just as accurate no matter what.

So I'm curious, these claims are either from a person that has no idea how an AR works and has never studied one or even looked at one or you're the engineer of the platform and know that the for end is a magical holder of the weight of the front of the gun (the barrel) without being attached to that weight in any way. Somehow to me the more this theory of a bull barrel will damage an AR is defended the more ridiculous it gets.

Let me point you in the direction of the Lewis Machine & Tool Company http://www.lmtstore.com/comple...s-firearms-guns.html makers of the finest AR's you can buy who offers a variety of "Heavy Barrels" for their guns. Are they subjecting their customers to certain gun failure by supplying them with the heavy barrel to cause failure?

The lower hangs from the upper, you've got it backwards.

Don't confuse accuracy with velocity. Shorter barrels are every bit as accurate, if not more so than longer barrels. If you compare any two barrels of the same diameter the shorter one will always be more rigid. As a general rule of thumb the more rigid a barrel is the less it vibrates, whips, oscillates, whichever term you wish to use to discuss harmonics.

The trade off though is velocity, shorter barrel gives you less time to burn propellant. If you are really wanting to step it out there you need as much velocity as can be mustered while maintaining accuracy of a given load.

I have always personally preferred short barels and most of my rifles are such. I have everything from 223 to 458 and all with varying barrel lengths. It was always my understanding (which is as often incorrect as it is correct) that for maximum velocity the barrel just must be long enough to burn all the powder used ,so developing maximum pressure. I also have always understood that longer barrels with iron sights were more accurate due to the longer sight radius but since I mostly use scopes this becomes rather irrelevant. I prefer the shorter length as it is my belief that they handle better for me. They just seem quicker on moving targets. They are definitely better handling in the field in thick brush and in getting into and out of a truck cab. I have never proven to myself tat long barrels were more accurate and really pay little attention to that aspect. If a load as shown in the book is adequate for the game I am hunting I go with that. In fact I really only load for accuracy and just plain don't worry about energy.I trust that the figures in the books have been well documented so I use them with confidence. I have never had a disappointment with a rifle /load combination in the field. I do have a couple of long barrels of 24" but most are much shorter some even down to 16 1/2". The only 2 customs I have ever commissioned have 22" barrels - one is 7x57 and the other is 257Roberts. Both shoot easily under 1/2". I think you should build what suits you for whatever your reason.

It's fairly simple. Velocity is your freind at 600 yards and beyond. 16" isn't your friend in the velocity department. I would be adding inches, to gain velocity and dope the wind a little better. Doesnt get much better than a 22" + barrel and a good 77gr bullet in a 7 or 8 twist that will load at mag length.

quote:

Originally posted by SMACK!!!!:
It's fairly simple. Velocity is your freind at 600 yards and beyond. 16" isn't your friend in the velocity department. I would be adding inches, to gain velocity and dope the wind a little better. Doesnt get much better than a 22" + barrel and a good 77gr bullet in a 7 or 8 twist that will load at mag length.

Yep, you're one of the ones paying attention. The thread is about what barrel for long distance shooting (tack driver at 600 yards) and it turned into "what's my favorite barrel length" with some misguided instructions like short barrels shoot best and AR barrels are free floating so your lower will be destroyed with a heavy barrel.

So I got my answer with confirmation from a high end barrel manufacturer and a top AR maker and a few folks here. But if you guys want to share your feelings on what barrel you like on your AR for what ever reason, go right ahead. My thanks to all who answered my question.

Personally I have shot and built a bunch of AR's over the past 20 years. As a purchase it outright barrel ready to go. It would be a toss up right now between White Oak Armarment and BlackHole weaponry when it comes to accuracy. Now if I was to purchase a blank and have it contoured, chambered and the extension installed along with the gas port hole being drilled. I would opt for Krieger or Bartlein. I would go with a 7 twist and shoot the 77gr Sierra's. But that's just me?

I'd opt for the bartlein as the first option.
you got things worked out in your head and have made a good choice.


btw a heavy barrel will droop under it's own weight even bedded into a bolt gun with a fore-arm supporting a lot of the weight.

quote:

Originally posted by SMACK!!!!:
Personally I have shot and built a bunch of AR's over the past 20 years. As a purchase it outright barrel ready to go. It would be a toss up right now between White Oak Armarment and BlackHole weaponry when it comes to accuracy. Now if I was to purchase a blank and have it contoured, chambered and the extension installed along with the gas port hole being drilled. I would opt for Krieger or Bartlein. I would go with a 7 twist and shoot the 77gr Sierra's. But that's just me?

A 77 grain bullet's ideal twist is 1 in 8, 1 in 7 is for 90 grain.

Well I bought it:

24' AR15 Varmint Upper Half, 5.56 NATO
Options: Stainless steel, 1-8 twist|YHM free float 4 rail with end cap:|Bolt carrier group & std charging handle:

I'll post the results when I get it dialed in.

Good to hear, I always like to go with a little faster twist than whats called for. I know a 7 twist with the White Oak and Blackhole barrels shoot the 77's like a fiend. Looking forward to your results.

Who's barrel did you go with?

quote:

Originally posted by SMACK!!!!:Who's barrel did you go with?

E. R. Shaw, if you go to their web site, you'll find their forte is accurate guns...therefore great barrels.

One of my most accurate AR barrels in the 6.5 Grendel chamberings I have had was from Alexander Arms but inside the barrel extension it was marked (E.R S).

quote:

Originally posted by SMACK!!!!:
One of my most accurate AR barrels in the 6.5 Grendel chamberings I have had was from Alexander Arms but inside the barrel extension it was marked (E.R S).

Hummmm sounds like E. R. Shaw to me, they're right here in the Pittsburgh area in a town called Bridgeville; I've been to their shop.

Got the barrel...

Shorter barrels are stiffer than longer barrels of the same diameter. It is easier to flex a long piece of tubing than a short piece. Most of the bench rest shooters and long range silhouette shooters I know use shorter heavy barrels like 20 inches rather than say, 24-inches. There are other factors, of course, but given everything else being equal, I believe a short barrel is more accurate. Shooting off-hand, a longer barrel may "hang" better, though.

Eager to see some 600 yard groups.

quote:

Originally posted by Calif. Hunter:
Shorter barrels are stiffer than longer barrels of the same diameter. It is easier to flex a long piece of tubing than a short piece. Most of the bench rest shooters and long range silhouette shooters I know use shorter heavy barrels like 20 inches rather than say, 24-inches. There are other factors, of course, but given everything else being equal, I believe a short barrel is more accurate. Shooting off-hand, a longer barrel may "hang" better, though.

That's why you do a heavy bull barrel; there's no way an 18" barrel will out perform a 24" bull barrel at 600 yards. I have never seen a long range target shooter use a short barrel; that's a square peg in a round hole.

quote:

Originally posted by Grenadier:
Eager to see some 600 yard groups.

More eager to find time on a decent day to even sight it in, it's high on my priority though.

You don't need to wait for clear weather. You just need to shoot between the raindrops.

All the guys I know who shoot long range silhouette shoot shorter barrels - 20 - 22 inches. At extended ranges, you need to dope the trajectory and wind, and a 150 fps is not a big difference. They prefer the more accurate short barrels. How much drop difference is there between a 2900 fps load and one at 2750 at 600 yards? You have to figure it anyway and a couple inches or a half foot is moot...you have to make adjustment or hold. Again - these guys are shooting off rests.

quote:

Originally posted by Calif. Hunter:
All the guys I know who shoot long range silhouette shoot shorter barrels - 20 - 22 inches. At extended ranges, you need to dope the trajectory and wind, and a 150 fps is not a big difference. They prefer the more accurate short barrels. How much drop difference is there between a 2900 fps load and one at 2750 at 600 yards? You have to figure it anyway and a couple inches or a half foot is moot...you have to make adjustment or hold. Again - these guys are shooting off rests.

By the same token, what's the big difference between 20 and 24"? Shaw is known for their accurate barrels and custom guns, they recommended the 24" barrel for my gun with what I want to do with it. I'm sticking with their advice and got the Shaw 24" barrel, I doubt I'll be disappointed.