Barrel Wear

[Hemingway]

I was reading a reloading manual today that said that it is possible for large caliber hunting rifles (nothing more specific was given) to have their barrels worn out anywhere from 500 to 1,000 rounds if factory-loaded ammunition is used.

That sounds like a ridiculously low number to me.

What do you guys think?

 

[sloughfoot]

Some calibers like the .243 are notorious barrel burners. Small bores with a large powder charge pushing that little bullet.

Even the .243 get a couple thousand rounds out of it before it is gone though.

 

[451_Detonics]

My 22 CHeetah which is a very much a case of an over bore cartridge went 3500 rounds before a noticeable drop in accuracy was noted. A lot will depend on how the gun is shot, if you sit and run round after round and get it hot it will wear faster, if you let it cool between shots barrel life will be better.

 

[Yeah]

Caliber, which here has become popular to conflate with chambering, has nothing really to do with it. Pressure and temperature are the real drivers behind throat erosion. It so happens that a good way to push temp and pressure is to put a big powder column behind a narrow bullet. I've had some whopper neck down boomer cartridges burn out throats in less than 1,000 rounds. A 22-284 will do it. So will a 7mm-338.

That long go lost its charm. Most of the old school, long casing, low slope shoulder cartridges, need too much barrel length to keep up with modern offerings.

 

[ryknoll3]

I think .220 Swift is another classic barrel burner.

 

[stack23]

500 rounds? ouch, i would not be happy

 

[Cannon]

Are the barrels getting burned up because of a fast twist rate? I've had people tell me that a good ar barrel with a 1/9 or 1/8 twist isn't even broke in till 1000 rounds. I know it's their opinions...

 

[Yeah]

Are the barrels getting burned up because of a fast twist rate?

No.

 

[Leo]

Sub 1000 round barrel life is a reality in the competitive world. Of course the barrels we threw away were more accurate than the average lower price hunting rifle is new. I would not even bother enter with a match with a rifle shooting over .75 MOA. A hunter can do well with a rifle that shoots 4.0 MOA. On the upper tier of compitition, things get very expensive

Heat and pressure burn the throat out of a barrel. It seems like stainless steel barrels have a better life than Carbon steel barrels, unless the carbon steel barrels are chrome lined. My 6.5mm X 284 rifle that I only used for 1000 yard matches ate a barrel every 800 shots. To save money, I designed a barrel contour that allowed the barrel to be unscrewed after about 600 rounds, and had my 'smith cut 2 inches off the breech end, rethread and re chamber. I also had him trim back and re crown the muzzle. That service was about $175, and a new HART barrel blank and the custom gunsmith work was well over $600, so being able to "set back" the barrel saved money without giving up accuracy. Low pressure/ low velocity rounds like 30/30, .348, .405 win and 45/70 will hardly wear the barrel at all, especially with cast bullets.

I have heard of people with very high performance rounds re-lapping the throat on a regular basis (ala Roy Weatherby) and letting the bullets jump quite a way before hitting a gently sloped rifling lead and having great results. That is found in rounds like a .220 swift, 25/06 or some of the 6mm calibers. Because I never shot those calibers, I never tried it.

Precision rifle shooting is expensive.

 

[Yoder]

I've always heard that properly breaking in a barrel will help it go more rounds before accuracy goes kaput.

 

[Cannon]

A fast twist rate would cause more heat and pressure in the barrel, wouldn't it? Don't even bother answering if it's an answer like "no." Trying to learn a little something here. Answers like that is why I've had 18 posts in two years. Thanks

 

[451_Detonics]

It might cause a slight increase but it would really be such a small increase at to be almost unmeasurable. The rate of rifling just doesn't really have an effect on pressure. I can have adverse effects on the bullets themselves which is why you need to match bullet weights and rate of rifling.

 

[Leo]

Your reasoning may bring up a scientifically valid point due to friction, but the increase in pressure and heat would be a very small factor compaired to the 45-55,000 lbs created at the point of combustion. Since the bulllet is leaving a two foot barrel at about 3000 FPS, the amount of time the friction could come into play would be an extremely short time. My prior experience is pretty limited, but I did have two 6.5mm rifles at the same time, one was a 1 in 8 twist and another was a metric rifle, but it worked out pretty close to a 1 in 10 twist, and both had about the same velocity with the same ammo. Neither had any pressure signs on the primer. It woulld be an interesting experiment to place a 1 in 7 twist .223 next to a 1 in 12 twist. You would have to have the same barrel length and same chamber to make it fair. I have never seen any data that suggests the maximum powder charge needs to adjusted according to barrel twist.
I have seen data requiring a specific twist rate to stablize a specific bullet, and I violated it by building a 1 in 9 twist barrel where a 1 in 8 was recommended. The rifle would not shoot those bullets worth a darn, but it shot a lighter bullet perfectly. Until that time I thought as long as you were within one or two it was close enough, but I was clearly wrong.

 

[Yeah]

I've always heard that properly breaking in a barrel will help it go more rounds before accuracy goes kaput.

No

 

[Yeah]

A fast twist rate would cause more heat and pressure in the barrel, wouldn't it? Don't even bother answering if it's an answer like "no." Trying to learn a little something here. Answers like that is why I've had 18 posts in two years. Thanks

You asked a simple question and I provided a simple answer.

The effect of twist rate can easily be deduced by looking at a reloading manual and noting the absence of max charge weights listed by twist, something that would be forced into print by liability were it a factor of any significance. One of my oldest 22-250AIs is a 1 in 14" and with bullets it will stabilize I run the same powder charges as a 1 in 8" cut with the same reamer.

 

[sloughfoot]

There are two things in a barrel that effect accuracy in an accurate barrel, the muzzle and the throat.

The muzzle is usually mechanically damaged to destroy accuracy. A damaged muzzle is fairly easy to fix.

The throat is eroded by the pressure and heat of the expanding gases. It is repaired by setting back the barrel. In other words, cutting out the damaged part and re-chambering.

Rate of twist has nothing to do with either.

This is my long version of "no". It is impossible to actually wear away the rifling between the throat and the muzzle. Copper on high grade steel, after all. The bullet gets worn down, not the barrel.

 

[Cannon]

Thanks for all the posts on this. I feel like I have a better understanding of what causes the barrel to be worn. I've been told that the military had to redesign the barrels on m16's because when they first were introduced they had a 1/12 twist and it caused the barrels to heat up significantly and burn up much faster then having a 1/8 or 1/9 twist when being shot full auto. Others have also said that because the design first called for a chrome lined bore and they chose not to go with it originally is what the demise of the barrel was at first. After hearing that I thought the possibility was there for a fast twist rate to cause excessive heat. I have just "started" to prepare for reloading and have been trying to read as much as possible to prepare. I've found someone that I'm going to apprentice under to get a good start atleast. Simply opening a reloading handbook has not even been a thought that passed through my head, honestly I did not really care about shooting paper accuracy until the last couple years. Even then I'm not going overboard with it, yet. Just reasonable sub moa is way good for me.

You asked a simple question and I provided a simple answer.

Yes you did. I did not say that you did not. The only thing I learned is you could swager into a thread and bounce out of it without any real contribution.

The effect of twist rate can easily be deduced by looking at a reloading manual and noting the absence of max charge weights listed by twist, something that would be forced into print by liability were it a factor of any significance. One of my oldest 22-250AIs is a 1 in 14" and with bullets it will stabilize I run the same powder charges as a 1 in 8" cut with the same reamer.

That's contributing, and I applaud you for it. Thanks.

 

[Leo]

Kind of related, there were several factors on the 1st bunch of m-16's and I am sure there are at least two 'nam vets here who will agree. 1)The early ones were plain steel barrels that did not like being rained on and living in the swamps of vietnam. 2) those years were full auto, making way faster heat build up than a person would normally require. 3) the original barrel was very thin under the handguard giving less mass to deal with the heat. 4) the powder in the early ammo proved to be unsuitable with the gas system. The rifling twist rate was pretty marginal for the bullet, especially if the velocity dropped down. The faster twist rate more reliably stablized different bullets, different weights and different velocities. I have never seen any reports that the heat and twist rate were related problems. I am sure I will get flamed here, but a 55 gr .223 bullet was asked to do too much without enough development time., and brave American men died because of it. Call me old fashioned, but I believe soldiers need .30 cal.

 

[Hemingway]

Thanks for all the posts on this one. This is an informative thread.