over heating barrels.... and warping?

[bainter1212]

My grandfather claims to have melted the barrel on an M2 carbine in Korea. His position was attacked by a large number of enemy troops and he just kept shooting the thing on full auto bursts, mag after mag. He says the bullets stopped hitting their intended targets so he threw the carbine down and grabbed another and continued firing.
After the Chinese blew the retreat bugle he took the carbine back behind the lines and had the armorer look at it.

The armorer confirmed that the barrel had warped and now had a nice curve to it.

So yes it can happen.

 

[jlucke69]

I used to have a Ruger heavy barrel varmint in 220 swift. After shooting a while, it would change it's point of impact up and right. I finally had a gunsmith put a ball bearing in the stock to add a little pressure on the barrel. This solved the problem and it would shoot the same all day long.

 

[Mr. Farknocker]

Not warpage

I don't think the problem is warping: at least not with respect to the way we weekend warriors use our firearms. A barrel sags (i.e., the amount of sag at the muzzle end of the barrel from the barrel as it exits the receiver) but even this is not "warping". The barrel may get hot but you've got to heat that barrel up to way over a 1000 degrees before it begins to "warp". What you call warpage is probably flex in the barrel. All barrels have a certain amount of flex and, hence, a given set of harmonics. They are designed that way. Handloaders fine tune their loads to match the harmonics of their barrel yielding more consistent shot placement. As the barrel heats up, the harmonics of the barrel changes, detrimentally affecting accuracy for most.

http://www.stocks-rifle.com/harmonics.htm

 

[gamestalker]

Back in the 80's I bought a beautiful M70 Feather Weight for my wife chambered in .270 win.. Up to about the 4th or 5th round it would shoot respectable groups. Beyond that groups, would drastically open up. Good hunting weapon, very poor range gun, IMO. It doesn't take much to damage or shoot the barrel out of a mountain rifle like this.

GS

 

[ball3006]

The point of shooting that many rounds rapidly is?

 

[pendennis]

Even the heavier barrels have difficulties. I own a one-off rifle. It's a 98 Mauser action, and it's been fitted with a Browning MG barrel, chambered in .30-06. I bought it because it was just too interesting to pass up.

It's really just a bench rifle, and I have a lot of fun with it at the range. I don't do any rapid fire with it, and I shoot only military match ammo and my own reloads.

The rifle barrel does stay cool longer than some of my other target rifles, but when the barrel of that rifle heats up, it stays hot much longer. More metal, more heat retention. Groups do open up, especially after fifteen or twenty rounds.

 

[bullseyebob47]

anyone found out how many rounds in a row until their ar15 or ak/sks accuracy is affected? .22 rifles? skeet shooters?

 

[627PCFan]

I've dumped 3 30 round mags back to back to back off a rest (milled ak) and no noticeable accuracy at 50 until the front hand guard got to hot to handle. Then things opened up because I went free recoil in the rest.

 

[Vikingsoftpaw]

Sustained firing of an overbore cartridge will cause accelerated wear of the feed throat. Basically, they will obliterate the start of the rifling.

Two calibers know for trashing barrels that way are the .22-250 and the .220 Swift.

 

[Kayaker 1960]

hot barrels

I have a Ruger M77 lightweight in .308. It has a pencil thin 16" barrel. It was fine for hunting but a pain at the range as I could only shoot about 3 rounds before the holes started walking up the target. 5 rounds shot without a break and they would be spread out about 8 inches in the 2:00 direction. I had the barrel Cryo tempered (frozen in liquid nitrogen) It's still no tack driver but it's much better. $60.00 well spent IMO.