over heating barrels.... and warping?

[bullseyebob47]

thats something i never thought about. my brother said if you shoot a high powered rifle like a .270 win. a lot the barrel warps and is not accurate. until it cools down?

years ago i shot 3 or 4 mags through a romain ak clone and it got so hot the gun oil on the barrel started smoking and even the wood became almost too hot to touch. i said "huh". and that was that.

hot barrels only effect high power rifle's accuracy? cause i remember shooting a lot with a shotgun while duck hunting but accuracy was not an issue. i have shot hundreds of 9mm rapidly with several pistols and don't remember accuracy being an issue. same with .22lr rifles. i remember taking my brother in law's s&w 15-22 and seven 25 round mags, shooting all rapidly with no accuracy issues that i know of. i was plinking, not shooting paper though.

does warp happen in ar15s? i know the ak47 clones get very hot. would those aks even make it through 7 or 10 mags without a cool down period?

 

[plmitch]

Interesting.

 

[jmr40]

Short answer, YES. Dating back to WW-1 soldiers manning machine guns have been issued spare barrels and gloves to handle the hot barrels. They rotate them often.

Some calibers are affected more than others. A hunting rifle like your 270 shouldn't be expected to maintain accuracy after more than a handful of shots. Depending on the individual barrel, very few. I used to own one of the pencil thin Remington Mt Rifles. It was always right on the money from a cold barrel. Shot #2 would usually touch the hole made by #1. Three shots were usually still under 1", but shots #4 and #5 would open up groups to 3-4". Considering the guns intended use that did not concern me.

Other guns are not affected nearly as much, but it is still there. A rifle like an AR or AK is intended for more of this type of use, but to a lesser extent will still be effected. Pistol rounds and 22's generate much less heat and will last longer before over heating. Same with 223 and 7.62X39.

Once a barrel gets overheated it will settle down after it cools, but some damage is there. Not really much of an issue with battle rifles where precision shooting is not a top priority. I would never let one of my hunting or target rifles get too hot. It will shorten the life of the barrel.

 

[buck460XVR]

Some guns are more prone to barrel heat than others, but heat, especially excessive heat will and does affect POI. This is why may target guns have heavy or bull barrels, as they are less susceptible and it takes more more rounds to heat them up. Many hunting rifles have thin light weight barrels because they are not expected to shoot high numbers or rounds in succession. Many folks when working a load for accuracy will disregard the first one or two shots until the barrel "warms up".

 

[Slamfire]

And yes, it happens.

I was discussing this yesterday at the range. I have a couple of very thin 64 Featherweights, those barrels walk when they get hot. The point of impact changes as they heat up. Also have a M1896 Swede, that thing walks 16" or more at 100 yards as it heats up.

I think this is due to internal stresses, perhaps barrel straightening activities, on these barrels. I was going to take the Swede barrel off and have it cryo treated, see if it made a difference, but I have shelved that project.

Heavier barrels will walk but to a lesser extent.

I am not a shotgunner but I don't see why the pattern won't shift assuming a severely stressed barrel. But, unless you pattern, how do you know?

Pistols, you would probably have to put one in a bench rest to see a POI change, AK47's !? don't know if anyone builds an accurate enough AK47 to see something like this.

 

[wilson]

How hot can you get a barrel before you lose the heat treating?

 

[ole farmerbuck]

I've always wondered why we see so many 22-250's with such thin barrels. In the summer while p-dog hunting, after only a few shots the barrels are pretty hot.

 

[230RN]

I had a Winchester 670 in .243 in which the barrel warpage with heating was very pronounced. Shot cold, it produced fine 2" groups with factory ammo, but a rapid succession of shots would walk the bullets high and left. I free-floated this barrel but did not cure the problem that way.

I loaned it to my son and he confirmed this effect.

Prior readings on my part indicated that with the barrel boring and rifling methods used at the time this gun was made, the bore would inevitably come out slightly crooked and they had to be bent back with a hydraulic press to bring them straight before turning the barrel to contour. This operation was gauged by eye by an experienced operator.

However, this left strains in the barrel which would lead to warping on rapid successive firing.

I imagine, but do not know, that this will not occur with hammer-forged barrels, since the forming mandrel would be straight in the first place, and also because the hammering would tend to relieve stresses, as well.

I've often wonderd if cryogenic treatment for stress relief would have eliminated that problem with this barrel, but did not get around to trying that before I finally got rid of the rifle.

Terry, 230RN

 

[bullseyebob47]

the ak47 from hell

http://www.youtube.com/watch?v=eNAohtjG14c

 

[mljdeckard]

It's not just 'hot to the touch' that would cause damage. It needs to be a lot of firing. In Germany we burned up a M-2 .50 cal barrel, it turned blue, they said it had lost its temper and needed to be scrapped. The CO was not happy. That was after a couple of hundred rounds of near-continuous fire. (It was already hot, and our dumkopf SMAJ decided to let his doofus driver shoot it some more, with no fire discipline at all.)

You can affect accuracy pretty easily with barrel heat, your groups will start stringing. But I think you are stretching the imagination a bit to say you would DAMAGE the barrel of a bolt-action rifle from sustained fire.

 

[rcmodel]

No, you can most certainly damage a bolt-action barrel with sustained rapid fire.

But it is not due to the barrel warping.

It is due to frying the rifling right in front of the chamber, or what is more commonly known as 'burning out a barrel'.

It is much easier to do with small bore high-intensity calibers like the .243, 22-250, .220 Swift etc. then it is with .223 or .308 type calibers.

I had a friend who completely burned out a barrel in one morning shooting prairie dogs without letting his new Model 700 6mm Remington barrel cool down.

rc

 

[ConstitutionCowboy]

My Ruger Security Six is the most accurate hand gun I own - until it gets hot. It could be the lug on the bottom of the barrel not heating and expanding as fast as the rest of the barrel - drawing it off target. I'm sure this gun is not much different than most in similar regards. It could be stresses in the barrel reacting differently to the heat, unequal cooling, different harmonics(vibrations) at different temperatures, etc.,etc.

Woody

 

[matrem]

That heating would happen far slower in a straight walled revolver round than in the "overbore" rounds the OP mentioned.

 

[rcmodel]

I can't hardly imagine a revolver getting hot enough to effect accuracy.

Or being able to shoot one well enough to tell if it did.

I'd be tired and weak after shooting one rapid-fire that much in one setting.
And then, my accuracy would suffer noticeably, for sure.

rc

 

[243winxb]

Some factory rifle barrels will walk when they get hot.

 

[cfullgraf]

Yes, I have a Remington 700 with a slender 17 Remington barrel. As it came from the factory, it would lose accuracy after only 4 or 5 rounds. Accuracy would return after the barrel cooled.

I did some work on the stock and the inletting and it goes a few more rounds now before accuracy begins to suffer.

Its a great rifle for carrying but I would not use it in a prairie dog town.

 

[Nickel Plated]

How hot can you get a barrel before you lose the heat treating?

I don't really know the exact temperature, but I'm sure you're gonna have rounds cooking off in the chamber long before the barrel gets permanently damaged. So when your gun starts shooting on it's own, it's probably a good idea to give it a rest.

 

[matrem]

I don't really know the exact temperature, but I'm sure you're gonna have rounds cooking off in the chamber long before the barrel gets permanently damaged.

Nope.
Do some research on throat erosion.

 

[ConstitutionCowboy]

That heating would happen far slower in a straight walled revolver round than in the "overbore" rounds the OP mentioned.

There's no doubt about that. However, the barrel of my Security Six gets too hot to touch after about 18 to 24 rounds - depending on how fast I put rounds down range.

Woody

 

[ConstitutionCowboy]

I can't hardly imagine a revolver getting hot enough to effect accuracy.

Or being able to shoot one well enough to tell if it did.

I'd be tired and weak after shooting one rapid-fire that much in one setting.
And then, my accuracy would suffer noticeably, for sure.

rc

It happens. I can.

Woody

 

[orionengnr]

And as far as heavy barrels go, remember:
Steel is not a great conductor of heat, but that works in both directions.

All that extra steel takes more rounds in a given time to heat up...but once hot, all that steel will take a lot longer to cool off as well.

 

[CA Raider]

technically - I think that a lot of the problem is that the barrel has not been properly stress relieved after it was manufactured. there are still residual stresses in the steel. these stresses, along with the heating (also causing thermal distortions) will cause the barrel to warp as it heat up. very good quality barrels should have less of a problem ... it's just that people don't want to pay for a precision barrel with stress relief treating (heat treating).

CA R

 

[twofifty]

It will happen, if you shoot them at warp speed.

 

[medalguy]

Many years ago I pretty much blew out a barrel in a Browning .30 ANM2 one afternoon with about 3,000 rounds fired as fast as we could get the gun to shoot 250 round belts. It was smoking at the end and the throat was just gone as was a lot of the rifling. The barrel was not new when we started but it was a good one.

 

[Tirod]

How hot can you get a barrel before you lose the heat treating?

That assumes they are. Given the examples of the M2 Brownings above, it should become obvious that a heat treated barrel would be annealed over 650 degrees, i.e. go soft.

With that in mind, gun designers, especially the ones working with self loading actions, deliberately DO NOT heat treat the barrels. You don't want a barrel engineered to be strong enough lose it's tempering from five or six magazines and then go soft - to have a yield strength less than what the chamber must endure.

Gun barrels aren't heat treated, they are left dead soft annealed and designed for strength by the mass of the material there. They have to, because shooters can and will exceed the limits of tempering in combat or at the range.

That avoids all the liability of a gun exploding using normal ammo excessively. As for the continual flame front of the case torching the throat and ruining the barrel, it's can't be, just delayed as much as possible by controlled firing. Shoot one enough, you will erode the throat, rifling, and gas port. Precision shooters simply do it at a much higher standard of accuracy, the military waits for it to open up to about 4MOA and then they might rebarrel it.

If you are shooting it enough to smoke the gun oil off the barrel, be more concerned about throat erosion and loss of accuracy.

As for causing the barrel to droop from excessive heat, it could happen. Colt did a video of shooting M4's to the point of destruction, the bullet finally pierced the barrel because of the severe arc in it.

If the barrel isn't from the better grades of material, an inclusion or portion with interior stresses will relax to a different shape than what was machined. Some can be literally bent back on target - it's exactly how shotgun barrels on doubles are "regulated." The labor is usually considered not worth it on a rifle and a new barrel is the result.

If it doesn't go on an auction site.