AR barrel heat, how much is too much?

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Jbird45

Jbird45

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I have had it driven in my head that heat is the enemy of barrels, along with rust and politicians.

That being said, while at the range last weekend I found out that an AR gets hot after a mag being fired at a reasonable pace. Not dumping the mag, but not waiting 30-60 seconds between shots either. It was my first time shooting an AR. I am used to shooting levers and bolt guns, as that is what I always had and grew up with.

I would like to assume these are designed to take some heat? Or am I wrong? I have a Ruger MPR with a free float barrel. I fired one mag and the barrel was hot enough I could only touch it for 2-3 seconds. After about 2 minutes it was luke warm. I take the mag out, leave the action open, and had the wind blowing through the barrel.

The guy in the stall next to me shot 3-4 mags in about 10 minutes and then cases his rifle and left.

Maybe I'm overthinking it, but I like to take care of my stuff. Is it best practice to let the barrel cool down between mags? Or are these things made to shoot a few mags at a reasonable pace before needing to cool?
 
“Hot” will deteriorate a rifle barrel faster than not hot - I think that statement is general consensus. Some consider a barrel a wear item - if it wears out for whatever reason, you replace it. If a barrel is used for (say) hunting deer, shot a couple times a year to verify zero and stagnant the other 50 weeks, it should last forever (which for a human is a lifetime).
I am never a barrel heater - I shoot to relax and for accuracy - I am never in a hurry. I see rapid fire and barrel burning as a testosterone thing just before the cold beer, the “F” word, and complaining about “the old lady”.
Heating/ using up lots of ammo and barrel life appears counterintuitive to marksmanship and accuracy to me but, to each his own (as long as I do not have to be around that behavior, I do not care).
 
Heat is not your barrels friend, however, you would need to get that barrel really hot in order to cook it out. While I rarely do any mag dumps, I do shoot at about the same pace as you're describing with my 223s. I've got several barrels with thousands of rounds through them, they're still accurate. Generally I keep my shooting to about 10-15 rounds before giving it a break, helps to take two or three rifles with you to rotate between. YMMV
 
Heat is certainly the enemy of your barrel, but you didn't buy an AR to fire one shot a minute. Or two, which is my rate of fire for chronographing or group shooting.

Competitive target shooters don't shoot all that slowly. When I was shooting F class, we got 20 minutes for 20 shots (or 22 minutes for sighters and 20 for record) but most of us banged out shots out in much less time so as to get them off before the wind and light conditions changed. A benchrest shooter trying to stay in one condition will shoot as fast as he can load his single shot and aim. But barrels are consumables just like ammo. One target shooting poster said your barrel should be considered shot out when the group size has increased by half.

Military and three gun standards are a lot looser.

The Luckygunner Labs test of brass cased/gilding metal jacket vs steel/steel were shot in rapid fire, but the barrels were not allowed to get hotter than 750F! The econoball ammo was not very accurate to begin with, not much under 4 MOA, but the Federal brass case stayed that way for 10,000 rounds. The Iron Curtain steel ammo started deteriorating sometime between 4000 and 6000.
 
Jim Watson said:
Heat is certainly the enemy of your barrel, but you didn't buy an AR to fire one shot a minute. Or two, which is my rate of fire for chronographing or group shooting.

Competitive target shooters don't shoot all that slowly. When I was shooting F class, we got 20 minutes for 20 shots (or 22 minutes for sighters and 20 for record) but most of us banged out shots out in much less time so as to get them off before the wind and light conditions changed. A benchrest shooter trying to stay in one condition will shoot as fast as he can load his single shot and aim. But barrels are consumables just like ammo. One target shooting poster said your barrel should be considered shot out when the group size has increased by half.

Military and three gun standards are a lot looser.

The Luckygunner Labs test of brass cased/gilding metal jacket vs steel/steel were shot in rapid fire, but the barrels were not allowed to get hotter than 750F! The econoball ammo was not very accurate to begin with, not much under 4 MOA, but the Federal brass case stayed that way for 10,000 rounds. The Iron Curtain steel ammo started deteriorating sometime between 4000 and 6000.
Click to expand...

You're exactly right. I didn't buy my AR to shoot the speed of a bolt gun, but I don't want to abuse it either. I will try to be conscious about heat, without driving myself nuts over it.

I have always been kind of over aware of barrel heat because of my over bore guns like my .22-250. Last time I was at the range I let some friends try it, and we shot 6 rounds in about 7-10 minutes, and the barrel was hot to the touch. I usually don't shoot that much, I do 2-3 and let it cool, but oh well. I would hope that barrel would be able to handle six rounds without permanently damaging it. But Everytime I tell a gun enthusiast I have a .22-250 and a .264 win mag they always say something like "you like to replace barrels eh?" Or they call it a barrel burner or throat toaster. I just want to make then last.
 
Even with pretty severe firing I’d expect a semi auto AR barrel to last at least 10k rounds.

If you’re the one paying for ammo the price of a new barrel is going to be noise compared to the price of 10,000 rounds.

If you’re not paying for the ammo you’re also probably not on the hook for a new barrel either.

I don’t dump mags to dump them, but if I need to shoot quickly during a match I don’t worry about it. A rifle is a tool, and tools were intended to be used.

BSW
 
The way I look at it there are three thresholds for “too much”.

The first is when the heat starts affecting where bullets hit, because the barrel metal is expanding. Depending on the rifle that could come after just a few shots, but generally it should take awhile unless you have a very thin barrel profile.

The second comes when it gets dangerous to touch exposed metal. If you end up burning yourself that’s not good.

The third comes when it starts causing problems with function, or causing damage to the gun (melting plastic parts, etc.).

Somewhere between the first and third you’ll start seeing accelerated wear, too, but - outside of a firefight - if you reach the first threshold you should probably slow down or change weapons.
 
Wheres that wristwister guy that used to get all worked up over some kind of barrel cooling tech that was gonna change the world?
 
I melted a M60 barrel or three in my time :D

It would take a lot of mag dumps/full auto fire to wear out most modern AR barrels. There is a very long post on another forum about high round counts of 100,000 rounds or more through AR's at Henderson Defense in Las Vegas. The owner has stated that the nitride coated barrels do just as well as the chrome lined barrels do under constant full auto shooting. They use uppers and lowers from most manufacturers and even the Palmetto State Armory uppers have held up under those extreme conditions.

I will gladly provide a link to that particular thread if the Mods say it is okay to do so. I Donn't want to cross post and stir up trouble.
 
Nature Boy said:
I used to worry about this but a knowledgeable fella on this site reminded me that barrels are a replaceable wear item like tires on a car
Click to expand...

I'll admit that I probably worry about it way to much too. My .22-250 and .264 win mag don't see a ton of use as they are vintage and I cringe at the thought of re-barreling.

But a modern AR is different I guess, and with a gun that is modular and made to be modified a barrel change is no big deal.
 
Jbird45 said:
I'll admit that I probably worry about it way to much too. My .22-250 and .264 win mag don't see a ton of use as they are vintage and I cringe at the thought of re-barreling.

But a modern AR is different I guess, and with a gun that is modular and made to be modified a barrel change is no big deal.
Click to expand...

Vintage, as in collectable, or sentimental value or just old?

Barrel makers and gunsmiths gotta eat too
 
Nature Boy said:
Vintage, as in collectable, or sentimental value or just old?

Barrel makers and gunsmiths gotta eat too
Click to expand...

The .264 is a pre 64' Winchester model 70 which was my grandfather's. So collectible and sentimental. I have owned it 4 or 5 years and have shot 18 shells out if it.

My .22-250 is a Remington model 700 ADL from the 70's. It was a co-workers fathers who recently passed. So not much of a collectible or a lot of sentimental, but it is still a nice gun.
 
The OP's Ruger MPR has a floating hand guard, as does my DDM4V7. You can only touch the end of the barrel, so if it's "three seconds" hot the the end near the chamber will be much hotter. I like to go to the range with three rifles and shoot 100-120 rounds of various calibers in about two hours. No guns get very hot this way. I admire the folks who shoot at a slow pace but for the $20 range fee, I want to shoot some guns!

I recently bought a new Savage 110 Varminter in 22-250 that was an erratic performer so I did my first barrel change and put on a Shilen barrel. To give the original barrel a good send-off I fired 40 22-250 rounds as fast as i could. I Had a few more rounds but it had started smoking after about 25 rounds and I was worried about damaging the plastic stock (it didn't).
 
22-250 is not 223. It has about twice as much powder for the same bullet. And 22-250 barrels aren’t chrome lines. And people expect sub moa accuracy from it unlike ARs where 2-3moa is normal

a 22-250 bbl might last 1000-1500 rounds before the velocity drops and groups open up significantly and you start seeing fliers.
If you just expect 2-3moa from your chrome lines AR you could prob shoot it fast for 20000 rounds before it has a problem.

that said, some ARs are cheaper than others and when the gun heats up it may not be as reliable if errors or shortcuts were taken in assembly.
 
I’d say my typical pacing with an AR is 1 round every 5-7 seconds. If I’m shooting drills the range limits speed to 1 per second, and shooting for groups probably no more than 10 seconds between rounds. Our club operates with a range officer, typically the first member on the line and each of us looks to shoot 2 magazines between target checks. 60 rounds in a span of 6-15 minutes with 10-15 minutes or so to hang targets. 120 rounds/hour. I often bring a muzzleloader and a rimfire Or two to keep things affordable.

So what if heat eventually kills barrels. Driving kills cars and I have no plans to walk to work.
 
For my S&W Sport AR I shoot what I want, as fast as I want (which isn't particularly fast) and I rarely give heat much of a thought. Per previous posts I consider the barrel a wear item. That doesn't mean I don't care at all. But if it gets pretty darn hot I don't care much. I do pay a good amount of attention to letting it cool off before I put it in its case.
 
Luckily re-barreling an AR is a relatively easy process and compared to the cost of the ammo it takes to burn out a barrel, pretty cheap. A good AR barrel is around a couple hundred, excellent is around $500.

In a match (3Gun) it's not uncommon to go through 20+ rds in under 30 seconds, times 5-6 stages in a day. Even at that rate a barrel lasts for many years for any degradation in accuracy is observed. How much the groups open up depends on the quality and thickness of the barrel. I'm running a relatively lightweight barrel now and I probably see a 1/2 - 3/4 MOA increase when it warms up, but no POI shift. Still accurate enough to stay on a 8" plate at 300.
 
The USMC training book (FMST 108) lists the maximum effective rate of fire for M16/M4 as 45 rpm in semi.

The sustained rate of fire in semi is listed as 12-15 rpm.

In a nutshell, you can shoot 12-15 rpm all day long without cooking a mil spec barrel.
 
You'll have to fire large amounts of ammunition quickly to get a noticable drop in accuracy if it isn't a pure target rifle.

The modern rifle barrel is designed to contain tens of thousands of pounds of pressure per square inch, plasma in the thousands of degrees, large amounts of friction from tight fitting projectiles and intense shock from the very quick burned powder.

Don't heat it up with multiple full auto beta mag dumps and you should be OK.
 
At an ambient air temp of 70 degrees F., an M4 carbine will reach cookoff temps after firing 140 rounds on auto at the cyclic rate. Even if this doesn't result in a cookoff, the temper in the barrel and bolt will be compromised.
 
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