Author Topic: Barrel life:powder burned (Read 713 times)

eroyd · « **on:** August 25, 2003, 06:19:34 AM »

If all other variables were considered equal, does the amount of powder burned through a barrel have a dirrect effect on the accuracy life of that barrel? For example, would a 7mm BR chambered barrel last longer than one chambered for 7-08?

Side question? Why does a 7 BR use a small rifle primer?

Iowegan · « **Reply #1 on:** August 25, 2003, 07:03:40 AM »

Bore wear and more importantly throat erosion, is more a product of case/chamber design and velocity. Example: you can expect 10's of thousands of rounds barrel life with cartridges designed for military use such as 223 Rem, 7mm Mauser, 308 Win, and 30-'06. A particularly bad one is the 264 Win Mag. Barrel life due to throat erosion is about 500 rounds. I can't speak for the 7 BR but I do own a 7mm-08. After a couple thousand rounds, the chamber and bore show no signs of wear or throat erosion. Shooting hot loads is a sure way to reduce barrel life in any rifle.

The small primers were introduced when Remington standardized the 7mm BR from a wildcat. It started out as a necked down 308 Win case with a large rifle primer. Who knows what their logic was on this?

Hcliff · « **Reply #2 on:** August 25, 2003, 11:43:48 AM »

Barrel heat is a major issue in wearing out a barrel. Hot barrels waer out quicker than tha smae amount of round through cool barrel. In general the more powder burned that faster a barrel will wear out because you are generating more heat i.e. .308 vs 300 weatherby mag. Also some people believe in the sandblasting effect.

Hcliff

Dave in WV · « **Reply #3 on:** August 25, 2003, 12:25:18 PM »

To add to Hcliff's comments, if you keep banging away and get the barrel hot it will wear faster. Letting the barrel cool and not overheat it helps for a longer life.

John Traveler · « **Reply #4 on:** August 25, 2003, 06:30:05 PM »

I've been involved with military testing of barrel life issues in small arms calibers up through medium cannon caliber (23mm through 30mm).

My associates run military small arms maintenance shops throughout Canada and the US in support of small arms competition and training programmes. We've used industrial quality optical borescopes, pneumatic air gages and electronic borewear gages in our tests. Firing tests run into the thousands or even tens of thousands of rounds starting with new barrels.

The following observations apply:

1. Rate of fire is WITHOUT A DOUBT the major determinant of small arms barrel life. Overheating barrel steel enhances the "blowtorch effect" of small arms propellant. Slower fire, allowing the barrel to cool off, increases barrel accuracy life.

2. Friction wear is almost insignificant, even when using cast iron and steel cannon projectiles. Bore wear measurements near the muzzle frequently show little or no change throughout the firing tests. Rifle designs that must be cleaned from the muzzle (U.S. M1 & M14) frequently suffer muzzle wear from improper cleaning, not firing.

3. Visible throat erosion and wear are the first indications of loss of practical accuracy.

4. "Overbore capacity" cartridges such as the .264 Winchester Magnum, are particularly hard on barrels. The relatively large powder charge and small bore enhances the "blowtorch" effect.

5. Chromium-plated bores can more than DOUBLE service life of barrels.

6. YES, barrel life was a factor in standardizing on military rifle calibers. The 7.62x51mm/.308 Winchester and 5.56x45mm/.223 Remington give notoriously long barrel life in sporting arms.