Throat/barrel burners
Okay I've heard several calibers referred to as being these things. So what are the calibers that you would classify this way and is it chamber or barrel erosion? How long is the life of the various guns? What exactly is the mechanism of damage?
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A barrel burner is a loose fitting term for a caliber which is designated as an "over-bore". There comes a certain point at which the powder burned/ignited, is super-intensified due to it trying to escape a hole which is basiclay so small as compared to the internal capacity,..that that super-intense flame erodes the steel of the "throat" at a much exagerated rate.
Are you familiar with cutting torches? What happens when you increase the oxegen and acetelyne and push it through the same small opening tip? It starts the red balls rolling across the floor right? That is a comparison to what a Barrel burner is.
Here is another way of looking at it,....take a 30-06 and a 30-378 wthby mag. Sit them side by side,...notice how much more powder capacity the 30-378 has? therefore that much more powder will be ignited and that much greater of a pressure will be created,...as both cases have to allow their respective compressed and superheated gasses to exit through a .308" hole. Then one with 3x the powder,..will no doubt eat the steel that is just in front of the case mouth,..and a very exagerated rate.
The throat is most always the area eaten away,..which will eventually lead to decreased accuracy. This happens becaause the bullet can not touch the lands(if you seated them that way) or it has a much greater "free-bore" area to jump across until it does contact the riflning,..and is then forced into it's spin. That jump,..although only ten thousandths of a second in real time,..allows the center of gravity to be changed from the direct center of the bullet, to which ever portion of the jacket which hits the rifling first,..in it's "cocked" angle which was caused by it having to jump that free space,..and after it was released by the case neck. That in turn shows up as wobble or "yaw" after the bullet leaves the barrel. That Yaw will take a greater and greater affect as distance is increased and the velocity is reduced. As a result,....your groups open up.
When this erosion becomes too great,...the gunsmith will "set-back" the barrel. This is taking some of the rear portion of the barrel off,..and then re-reaming the chamber. That allows the throat reamer to get forewrad into new rifling that has not been eroded yet,..and the eroded portion has now been replaced by the "lead" or "neck" area from the chamber being cut further foreward. The barrel loses some length,..but usually it can be done with less than 1" of length lost. A freshening of the crown,..and you are back in business.
My gunsmith took several swiss sniper guns in 6.5x55 with 10,000rnds through them,...set the barrels back, and recrowned the, and to this day, he says those rifles are still shooting 1/2" groups in the hands of their owners who couldn't be happier with what they got for the price. The rifling doesn't wear out per se,...it is USUALLY the throat area and rifling at the crown or muzzle exit which wears down from the escaping gasses. Freshen up both and start shooting again.
This is why the larger powder capacity cases always will burn a barrel faster than a smaller capacity case,...when both calibers are the same. I.E. 300win vs 308.
hope that helps some. I am sure I have missed a few things and several of the posters here should help to set any discrpancies straight.
why chase the game when the bullet can get em from here?....
Got Balistics?0 -
It's usually the small caliber high powered cartridges that do this like the .300 win/mag where you are forcing all that burning powder and pressure down a small bore. You can basically count on most bottlenecked high powered cartridges doing this to some extent more than a strait case cartridge.
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Your life is not my fault.0 -
AS A VERY GENRAL GUIDE .308 MATCH BARRELS ARE REPLACED (OR SET BACK)AT ABOUT 5,000 RDS., NEXY SIZE UP (UP TO .300 WIN.MAG.) 1,500/2,000 RDS., BIG BOOMERS (.30/378 ECT.) 800/1,000 RDS. 0 -
JUSTC: Is purrty darned thourgh, and leaves nothing to add or argue about, (shucks). I can give an Example of a Barrel Burner: .264 Mag, and .220 Swift. Probably the most famous two of all time.
Things that will help extend the life of a barrel: Moly Coating the Projectiles, and seating to the maximum length when reloading.
I have a Friend (ex-Military U.S. Army Marksmanship Team - Retired). This Gentleman had a 98 mauser in .308, Fiberglass Stock, Timiney Trigger, 20" Heavy Barrel at 1 1/4th inch dia. It would shoot like a House afire. And he swears to the Fact: At one time, while shooting a 24 inch Barrel over a length of time, he competed with it after 12" were shot out. [^]
Ronnie G. Perkins0 -
Cleaning regimen and barrel cooling become paramount in importance when shooting the boomers.
why chase the game when the bullet can get em from here?....
Got Balistics?0 -
But then again, I have a stock Model 700 in 7Mag made in '62 or there about, it had been blueprinted and trued. I got it second hand, it has had about 10,000 rounds thru it, got "lots" of freebore, you can see about .5 of erroson on the throut, and it will shoot 1/2 groups all day long with bullets seated to book OAL. Go figgure!!
SEMPER FI MAC, SEMPER FI0 -
Pack Rat,..I have talked to guys who have 8000 rnds down the bore of 308's and other calibers who are still cutting a large one hole group. Some barrels just plain shoot...........
why chase the game when the bullet can get em from here?....
Got Balistics?0 -
you can add the new winchester super short magnums to the list of thoat burners according to a fiend who is trying them for benchrest 0 -
another thing the 264 and the 220 swift both got their "rep" when barrel steel was not nearly as good as it is today. neither is as bad as many would have you think 0
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