How many shots before cooling the barrel?

Does off welcome to the forum. I've only had my AR since early March it has about 1k rounds through it. I have only 2 10 round mags, NY infringement , I usually shoot 1 mag and reload it keeping the other loaded. I usually shoot slow for groups, but have done mag dumps as well.

I also take two bolt actions along and shoot to 300 meters and shoot them after a few mags.

I recall an Army publication, from back in the '70s, that stated that 12-15 rounds per minute was the maximum rate of fire at which the M-16 can be fired indefinitely without damage to the weapon or experiencing cook-offs.

I have a bolt gun for prs (308) that I spent too much on. I when I am doing bench work I try to keep the barrel cool enough to be able to put my hand on it

Then in a competition I’ll put 12 shots down range in 70 seconds and not think twice about it ‍

Honest opinion, shoot as fast as you want, recognizing that getting it super hot is a little harder on things than slower firing

More importantly, focus the mind and discipline the body so that every shot adds value to you as a shooter, when the 223 barrel dies, you will have shot enough to buy another few barrels

RedLeg105 said:

I recall an Army publication, from back in the '70s, that stated that 12-15 rounds per minute was the maximum rate of fire at which the M-16 can be fired indefinitely without damage to the weapon or experiencing cook-offs.

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I can tell you with absolute, 100% certainty that that is complete BS if we're talking about a half way decent quality, modern AR15, M4 or M16.

Depends on how hot the barrel gets. A barrel that’s too hot to touch is too hot!

whatnickname said:

Depends on how hot the barrel gets. A barrel that’s too hot to touch is too hot!

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Nonsense. Steel can easily burn skin at temps under 150 F. That sort of temperature isn't going to hurt the barrel in the least. You can literally get a gun barrel too hot to touch by just leaving it in the summer sun.

RedLeg105 said:

I recall an Army publication, from back in the '70s, that stated that 12-15 rounds per minute was the maximum rate of fire at which the M-16 can be fired indefinitely without damage to the weapon or experiencing cook-offs.

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I imagine a whole lotta M-16 got cooked in Nam, my Uncle spoke of the new 16 in a letter from Vietnam they really liked them. ( edited to family version)

Varminterror said:

Fixed it for you.

Good rifles don’t have temperature shifts. Almost any barrel will shift a bit from clean to sustainably fouled, but if temperature causes your barrel to walk, send that rifle walking.

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I will disagree with this statement.
My Tikka 308 after 10 consecutive rounds will exhibit point of impact wandering a bit, I consider this perfectly normal as the thin barrel heats up to an uncomfortable to the touch temp image how hot the inside is...

taliv said:

Run your ar wet. Oil not grease.

The amount of time you wait is situationally dependent. E.g. benchrest shooters often shoot as fast as they can because they want to shoot all their rounds in the same wind condition and their barrels don’t shift much when they heat up.

However the downside is that throat wear will accelerate when you’re firing fast. Your barrel won’t last as long but that just makes competition a more expensive hobby.

Doing a couple mag dumps is not good for extreme accuracy but it won’t keep you from making head shots at 400 yards.

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Are you advocating oiling the bore or just the moving parts? I don’t want to jump to conclusions here so perhaps you’ll clarify.

bearcreek said:

Nonsense. Steel can easily burn skin at temps under 150 F. That sort of temperature isn't going to hurt the barrel in the least. You can literally get a gun barrel too hot to touch by just leaving it in the summer sun.

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Well you just go ahead and shoot yours to the point that you can fry an egg on it. Doesn’t matter to me how many barrels you wash out. When mine get too hot to touch, I let them cool down. I find that I get better barrel life with my system.

South Prairie Jim said:

I will disagree with this statement.
My Tikka 308 after 10 consecutive rounds will exhibit point of impact wandering a bit, I consider this perfectly normal as the thin barrel heats up to an uncomfortable to the touch temp image how hot the inside is...
Send my rifle walking? Probably not today

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Keeping a rifle with irregular internal stresses, either due to inconsistencies in stress relief in the barrel, or non-planarities in the machined mating surfaces is your choice.

I’d either have it trued, or send it packing. Guys use the “it’s a sporter barrel” excuse to defend their rifles too often, as if it actually explains a justifiable defense for machining mistakes or lack of stress-relief in production (or poor stress relief, if it was included). It’s a lame excuse. There’s no reason to tolerate a walking sporter barrel any more than a varmint barrel.

But lots of guys like their rifles, and lots of hunters never get their barrels hot, so it’s not relevant for their life. I’d send it down the road.

whatnickname said:

Well you just go ahead and shoot yours to the point that you can fry an egg on it. Doesn’t matter to me how many barrels you wash out. When mine get too hot to touch, I let them cool down. I find that I get better barrel life with my system.

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Do you have documentation of your system which supports improved barrel life under the same conditions, with only changing the rate of fire (aka, max barrel temp)?

Varminterror said:

Keeping a rifle with irregular internal stresses, either due to inconsistencies in stress relief in the barrel, or non-planarities in the machined mating surfaces is your choice.

I’d either have it trued, or send it packing. Guys use the “it’s a sporter barrel” excuse to defend their rifles too often, as if it actually explains a justifiable defense for machining mistakes or lack of stress-relief in production (or poor stress relief, if it was included). It’s a lame excuse. There’s no reason to tolerate a walking sporter barrel any more than a varmint barrel.

But lots of guys like their rifles, and lots of hunters never get their barrels hot, so it’s not relevant for their life. I’d send it down the road.

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I’m going to disagree with you on this once again.
(Unless of course you have personal test results that support your post.)

Jim

Varminterror said:

Do you have documentation of your system which supports improved barrel life under the same conditions, with only changing the rate of fire (aka, max barrel temp)?

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When I shot competitively I kept extensive notes on barrel life. Those rifles that were shot without regard to how hot they got had a much shorter barrel life. I’ve gotten my M1 Grand so darn hot that it boiled the oil out of the handguard. That aside, you have access to documentation on this issue too. Just Google the development of the 264 Winchester Magnum. That one had a reputation for washing the throats out of barrels in as little as 2000 rounds. This was the round that forced Winchester to come up with the first stainless steel rifle barrels back in the day. Then the lightbulb came on: Let the barrel cool down and barrel life is extended. Even the reloading manuals today allude to this fact. Read the section on the 264 Winchester Magnum in edition 10 of the Hornady Reloading manual...page 342 paragraph 2 addresses this issue. Another case in point is the 22 AI or 223 X 57 (6MM case necked down to .223). I’ve seen that one shoot barrels completely out in as little as 1500 rounds. That kind of sizzling velocity comes at a price...barrel life! And the chief culprit is heat!

taliv said:

Uhh no. Just the bolt carrier group. Try to keep it out of the bore.



I don’t have documented proof or know what his system was but it’s widely accepted that faster rates of fire erode the throat faster than the same number of shots in slow fire.

I can give you one anecdote. In 2011 I shot a match at camp butner in hurricane irene using the 240 machine gun qual course electronic targets (“Ivan’s I think they call them). The entire match lasted 2-3 min give or take. I can’t remember but it was fast. My barrel wouldn’t shoot under a minute after that.

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Back in the 60s and early 70s when I shot competitively I had a good friend and mentor that had long since been a Distinguished Expert. He was a national class competitor and a master gunsmith. He came up with a 30 caliber, aircraft machine gun barrel that was made out of an alloy he called stellite (sp?). Said it was so tough you couldn’t cut it with a torch. You could heat it cherry red and make it crumble but you couldn’t cut it. He told me that no one knew what stellite was as the composition was a military secret. He threaded that thing and put it on a Winchester M70 Target model and shot the Palma Match with it for years. Looked pretty funky with that big knot out on the muzzle end. He got some unbelievable life out of that darn barrel as I recall. No idea where he came up with that barrel but he was x-military and knew quite a few people on US Military Marksmanship teams. That barrel was much more resistant to heat than anything I had seen before or since.

@whatanickname - so you have more statements here claiming barrels can burn out fast, but other than these anecdotes, you didn’t share any data to specifically and objectively show proof of grossly slower rates of fire increasing barrel life. When you mentioned your “system,” I assumed you had objective proof, as in recorded barrel life and load data for multiple barrels.

It’s a fair observation - shooting high volumes of overbore cartridges will burn out barrels - but I haven’t been able to produce data which reflects a barrel which hasn’t been “shot to get hot,” will last significantly longer than one which is shot quickly. Personally, I haven’t been able to prove it to be true. In shooting 243’s (and AI’s), 7mm RM’s, 223/5.56’s, and 6 Dashers to their death both in competition and in hunting rifles, I haven’t had a barrel which was never allowed to get hot last any longer than the standard deviation of what any barrel might have lasted. Certainly takes a LOT longer to burn out barrels when you only shoot a couple hundred rounds per year instead of couple hundred per month. But I REALLY believed my 243AI coyote rifle would last twice as long as my bench rifle - in round count - but it burned out at roughly the same roundcount as the others which were “abused”.

I’ve seen and read and heard all of the conjecture about saving barrel life - using slower burning powders to reduce heat, single base powders, lower velocity loads, lower pressure loads, using faster burning powders to reduce the strain-time, letting barrels cool for X minutes between shots, reducing cleanings, nylon bushes vs. brass vs. no brushing, different solvents, carbon steel vs. stainless (since stainless is more brittle and more prone to wear - contrary to the common statements about 264win), cut vs. button rifles barrels, setting back barrels, chasing lands, gain twist, ratchet rifling, etc etc... so many things folks claim will dramatically increase barrel life... but in practice, almost none of it seems to pan out in any objective, repeatable, and recordable way.

Stellite is a cobalt-chromium alloy. The US military has been using them in various machinegun barrels since just after WWII. The stellite is a liner made separate from the rest of the barrel and then usually cryogenically cooled and hydraulically pressed into the barrel. Some times another piece of steel is then put in behind the stellite where the chamber is then machined, sometime the chamber is machined into the stellite. The stellite liner typical goes about 15-20 calibers down the barrel from the chamber. Since the stellite liner has to have the riflings machine in before it's inserted into the steel barrel it takes specialized presses that can hydraulically insert the stellite liner and ensure the rifling in the liner lines up with those in the steel barrel.

taliv said:

it’s widely accepted that faster rates of fire erode the throat faster than the same number of shots in slow fire.

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I absolutely agree that it is widely accepted. I just haven’t been able to source ANY data which supports it, and my own personal experience hasn’t aligned with the prescribed paradigm.

My personal experience is burning out only a handful of barrels which were NEVER allowed to get hot - always following those rules of 2-5min between shots, against a few dozen barrels in the same time of different competition barrels which were thoroughly abused for rate of fire and barrel temp. My coyote and varmint rifles, intentionally “babied,” should have lasted hundreds or maybe even thousands of rounds longer than my match rifles.

What nobody has been able to answer for me: if slower fired barrels last longer than rapidly fired barrels, why didn’t any of mine?

The particular cartridge and it operating pressure and gas volume has a lot to do with it too, in addition to the rate of fire. Compare throat erosion of a moderate pressure cartridge like 35 Remington to a "barrel burner" like 22-250. If they both are made of the same material and get shot at the same rate of fire (fast or slow) you would expect the 35 Rem to have much longer barrel life than the 22-250. The higher the pressure the higher the gas temps and the greater the gas volume the more high temperature gas you have to erode steel.

I won’t speak towards rapid fire burning out a barrel faster than slow fire, However I will say that I have noticed increased throat erosion seems to go hand and hand with increased powder charges.
No scientific test results you understand rather just an extra thousand every couple hundred rounds when checking CBTO type thing.
Does that count ??

I have seen A4s and such run very hot due to necessity. If you're not duckin, don't run more than a full 30 rounder without giving it a break.

Anderson says to run their guns dry due to a proprietary metal (F85 I think) treatment. I think they sre the only ones to say that. Don't do it! Don't be cheap with the CLP and use quality lubricants.

Just $0.02 from an old fat guy!

Don't run your car without lube either!

taliv said:

I’mnot suggesting they last longer. I’m suggesting rapid firing schedules last shorter.

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I assume I’m misinterpreting something in your statement, so please bear with me....

First, this topic is more of “an itch I can’t scratch” than something I really feel passionately about. The widely accepted notion is logical, and in a physical sense, it sure seems like it should be true. I have SOME engineering based reason to doubt the truth, but the systems are different enough, my mind accepts that each could be a law unto themselves.

But I believe in data. My own dataset doesn’t support the widely accepted notion, but I recognize it’s not an exhaustive dataset - so I keep hoping someone has such to either confirm or disprove mine.

What I believe I have is two-fold: 1) a relatively substantial experience in burning out barrels in conditions where the competition format or my own shooting pace yielded barrels “too hot to touch,” and 2) a limited experience in burning out barrels under less strenuous, slower fire conditions where my barrel never even got warm to the touch, following those guidelines of 2min or more between each shot. Short-hand: I’ve burned out a lot of barrels shooting fast, and a few barrels shooting slow.

What I’ve observed is also two-fold: 1) the standard deviation of barrel life is pretty high, and 2) lifespan between a fast fired barrels and a slow fired barrels aren’t statistically different.

Resultingly - my assumptions about this divergence of my personal dataset from the widely accepted notion have to be two-fold: either 1) there’s something wrong with my personal data set, or 2) the widely accepted notion isn’t true.

So I ask for data whenever I see someone who claims to have a “system” or otherwise implies a depth of data to support the widely accepted notion that shooting fast burns out barrels shooting slow. So far, in ringing this particular bell several times for over 10 years, nobody has been able to provide data to support it. So my dissatisfaction continues, and my brain continues to itch.