A while back I remember reading somewhere that the idea that letting your barrel get hot via rapid shooting would ruin the barrel was a myth.

I beleive they actually took some temps and the net result was that the bore/chamber temperature spike upon firing a round was measured in hundreths (maybe even thousandths?) of a second, and that there was no way you could overheat a barrel of non full auto gun.

This of course isn't about accuracy or changing POI, but the basic idea that you need to be really anal about letting your barrel cool for fear of "frying" the barrel...

Does anyone else remember reading this or have any data?

Maybe it's one of those hallowed wives tales...

... I don't believe it is a myth... excessive heat is supposed to be what ruins barrel throats.. everything I've read by prarie dog shooters indicates that rapid, continuous firing will wear out a good barrel in VERY short order, but if the barrel is allowed to cool between shots, or to NOT get too hot, it will last a long time.

Hornetguy,

You just summarized what I've always believed/followed. Rotating rifles in PD towns, trying to not let my barrels get too hot.

But how do we really know?

The chamber gets REALLY hot when the round goes off. there's no comparison even if it was several hundred degrees between shots that wouldn't mean much metallurgically (OK you engineer types, weigh in here...). Throats erode from the powder burning and pressures combined--so what happens between shots that matters? How cool is cool? I think it might be one of these things that we take as gospel that there's no real data to back it up....I'm looking for some science here...

[ 02-13-2003, 09:13: Message edited by: rogerinneb ]

I sold Tricon wear resistant steel for 7 years. Temperature and impact were nearly equal in accelerating wear.

We ran extensive test under all kinds of conditions and found that alloy steel at 200 degrees over ambiant wore nearly four times as fast as room temperature steel.

That's why "Super C", a chromium carbide overlay material was developed for the coking plants at steel mills and the kilns in cement plants. Wear was nearly the same as room temperature up to 800 F. with the 72 Rc overlay on A-36 mild steel.

I've seen a Swift barrel toasted beyond hope with 200 rounds on a hot day in a ground squirrel town.

Throat errosion is a direct result of heat and pressure. The higher the pressure, the higher the heat, the quicker the errosion.

It is said, that the flame temperature of cartridges above 40,000 psi, is above the melting point of alloy steel. When you fire a round, the surface of the steel in the area of the throat is immediately subjected to a blast of searing heat, which quickly dissipates after 1 firing.

Successively fired rounds compound the problem of heat damage within the area of the throat due to high heat saturation. Rapid fire sustains these high temperatures, increasing the length of time that the throat is exposed to the cutting forces of heat and pressure.

The military chrome lines their barrels to reduce the effects of heat damage brought on by rapid fire. The high nickel content in Stainless Steel is thought to help to reduce this damage as well.

When it comes to shooting high pressure rounds, there is really no way to prevent this damage unless you were to quit shooting altogether. Since this isn't a viable option, then next best thing would be to try to keep the barrel to point where you could grab on to it with your bare hand without losing flesh in the process.

Varmint hunters are going to get their barrels hot when amidst a active PD town. They just have to accept the fact that damage is going to occur and deal with it. Rapid fire means rapid wear...

Malm

Ive had a bore scope down the barrel of quite a few weatherby cartridges. Under magnification the throat and about an inch forward looked like mud flats when the tide goes out. Hundreds of little cracks in the steel. The barrels were no good.

Ever wonder why machine-guns have extra swap barrels? There's your answer.

RSY

It's not a myth. Heat transfer (from the bore surface to the mass of the barrel) is directly proportional to the temperature difference. In other words, the bore surface stays hot (real)longer in a hot barrel.

Which brings up stainless barrels. Stainless steel does not conduct heat as quickly as carbon steel does. So?

Does anyone remember an old American Rifleman article about barrel erosion ? It was a bit technical for the non metallurgist but was a detailed study of the problem . First erosion technically is a mechanical process. So erosion is not the proper name because the process is one of the steel at the very high combustion temperatures absorbing carbon which is present in the hot gases. You the create a layer of high carbon steel in the bore. In the heating and cooling of the barrel this layer begins to develop cracks . This is the " erosion" that is seen. For the layman it means the more rapid the fire the more "erosion" - slow fire means cooler barrel, less carbon absorbtion , longer life.

I have started testing my barrel by holding my hand on it.If it gets too hot to hold for 3-5 seconds then I let it cool.I don't know if it is right or wrong but thats what I do.FWIW
Jeff

[ 02-13-2003, 22:38: Message edited by: JeffP ]

What about when your cranking the rounds through lever guns such as I do with my 45/70 and .44 rem mag ?? Are these types of rifles affected as well I mean I know to some degree thye would but I imagine not to the same degree a 22/250 would be ??

44 Mag is considered to have high pressures for a pistol cartridge, but at 35,000 psi it is very low for a rifle cartridge. Same for the 45/70; as a former black powder cartridge with many old rifles still in the hands of shooters the factory pressure levels are very low, and even the commercial "high" pressure loads don't exceed 40,000 psi. This much lower pressure level results in less wear of the barrel. The much smaller ratio between the cartridge case capacity and the bore diameter also means that the pressure levels will fall much faster in a 44 Mag or 45/70 than in a 22-250 etc.

Less pressure yes, but a 45-70 bbl gets very hot very fast, Too damn hot to touch. Lots of powder in there.

Johnly - I think you hit the nail on the head. It depends on what the meaning of the word "ruin" is. I've had several rifles that I owned in my life so hot the stocks were smoking with no significant effect on accuracy. Perhaps this is something the benchrest boys should lie awake at night worrying about...but I question it in the real world.

If I have to worry about never letting my rifle barrel get over 200' I might as well stay home.

I think this is a tempest in a teapot. I know lots of guys can spout data from lab results yadda, yadda....but like I say in the real hunters world it amounts to a fart in a whirlwind.

With using the tactile temperture senser. I would have to say the a m-14 barrel can get hotter sitting out in the August sun then from a normal rapidfire string in a highpower rifle match.
Ray

P.S. Can't say the same for an 8mm mauser fired as rapidly as possible for five minutes straght. The cosmoline started melting out of the wood and smoke came out from under the handgaurd.

there's NO myth..
1: every bullet you fire does 3 things, heats the action, blasts crap down the barrel (ejecta) and stretches the action.

2: steels are easier to "work" or abraid when hot... which is why you can FORGE steel...

3: the ejecta is MORE abrasive than me chasing a troll

4: when the steel is hot, MORE is abraded... and the hotter, then more

I've seen DORKS throw 20 rounds down their wizbang autoloader, pop in another clip, and BITCH that the smoke from the stock is ruining their shooting. As I own a couple autos, i just sit back, sigh, and think "wow, a 308 from my m1a puts MORE heat into the chamber than on my bolt gun, as the barrel is thinner" and think that there's NO way I would shoot 20 from my bolt gun in 1 min... or an hour
jeffe

I've sen M60 machine gun barrels start glowing in the dark under high volume rapid fire conditions. They actually droop under their own weight, to a certain degree. When we got 'em that hot, and believe me, it happened, we surveyed them the first chance we got!