Barrel life, Bob's 7x08's and other's experience

More expensive to feed, but worth it.
ywltzucanrknrl
A Poster
A Poster
Posts: 203
Joined: Thu Aug 06, 2009 3:41 pm

Barrel life, Bob's 7x08's and other's experience

Post by ywltzucanrknrl »

I'm always interested in barrel life with respect to useful accuracy. Bob's comment about his two 7x08's with 5,300 rounds was impressive, especially since it sounds like he feels they are still his best rifle/barrel combination. Bob McAlice, what barrels are they and how accurate are they? Who else has documented experience with barrel life (maker, number of rounds, loads used....) that they would share? I'll admit, I didn't start keeping good records except for the XTC service rifles I shoot, until recently, and the last Green Mountain barrel (1 in 7 twist, button rifled, 223, 77 and heavier bullets with Rl 15) was done just shy of 3,000 rounds. I'm keeping good records now, but don't have enough rounds through the high power rifles to get a good idea of barrel life vs accuracy.
Jon
Cody, Wy.
Bob Mc Alice
Expert Master Poster
Expert Master Poster
Posts: 1772
Joined: Mon Sep 11, 2006 6:54 am
Location: Colorado

Re: Barrel life, Bob's 7x08's and other's experience

Post by Bob Mc Alice »

Jon, they are Douglas premium XX stainless in a #3 and #5 contour. I bought them in the FTC condition and fitted them myself. The last time they were used was at 2016 Nationals, Raton. On the off day my spotter witnessed both rifles print three shot nickle size groups at chickens and tennis ball size at rams. That is very good for their mileage. I hope to get another few of seasons of useful accuracy with them. I have yet to shoot out a stainless barrel. Others have told me to expect up to 8000 accurate (competitive) shots. That Winchester M70 I have was a .243 Featherweight with a carbon barrel. It went south in accuracy at 2270 shots. I fitted it with a new Remington 700 stainless takeoff barrel in 7-08..ala Remchester.

This is my slave rifle. It gets fired a lot of rounds at a time and often. It often gets hot to the touch and stays that way for numerous shots. I do not care, it won't melt. It is my go to gun for windy conditions at CRC matches. Why throw half your shots into the dirt with a good rifle? It often goes on camping trips with us with a couple hundred rounds. We like to stay on the rugged BLM lands in the area. It has exactly 5492 shots fired and still as of two weeks ago off the bench printed 2.0 inches at 300 M. It mostly fires 41.0 grs. IMR 4320 with a 140 gr. Sierra FB spitzer. The bore scope shows major wear but it still shoots well. It wears a Leupold 12x with knobs and 1/8th dot. It will be a sad day when it is done, I love shooting that gun.

I have shot out four Remington factory carbon 7-08 barrels in my life. The magic numbers at time of death was in the 4800 - 5200 range. One with high mileage went from from shooting 2.5 inches at chickens to ten inch groups at same distance in less than 40 shots. It gave out real quick. One had bad steel with lots of inclusions (impurities) that went south at 2700 shots. It is not even deer hunting accurate.

I also wore out a Ruger 7x57 carbon barrel at 4800 shots. It had a steady diet of RL-15 driven 140 gr. Sierra spitzers. It now wears a Remington 7-08 carbon take off barrel with 2082 shots on it.

I have kept accurate records of barrel life for a long time. My entire rifle collection has known shots fired records. It is just the way an OCD person operates. :D

....one more added tidbit thanks to my record keeping. Since buying my first 7-08 in 1990 I have fired 47,411 rounds of that cartridge.
Last edited by Bob Mc Alice on Tue Mar 07, 2017 8:58 pm, edited 3 times in total.
topclass
A Poster
A Poster
Posts: 212
Joined: Sun Apr 03, 2011 9:06 am
Location: Central Texas

Re: Barrel life, Bob's 7x08's and other's experience

Post by topclass »

Interesting real world numbers. Another forum I follow talks about barrel life in terms of 5-10 seconds, which doesn't sound like much, but when one computes a bullet's speed and the length of time in the barrel, a number between 4-6,000 rounds is suggested (using 2500 fps), which jives.
Snake
AAA Poster
AAA Poster
Posts: 863
Joined: Wed Jul 07, 2010 12:37 pm
Location: St. Louis, Missouri

Re: Barrel life, Bob's 7x08's and other's experience

Post by Snake »

By barrel life we are referring to the accuracy life/usable life of a barrel. As an anecdote one of our regulars had his 7BR re barrelled on account of the years old barrel quit shooting under 1.5 in...and it got really weird at long range. He had 25000 plus rounds through the old barrel. We sectioned the breach through the chamber area part way into the rifling (what was left of it) The throat had eroded over 2 inches beyond the leade---it looked almost like a smoothbore with faint rifling reappearing gradually. However the last three inches at the muzzle were relatively ok....and that's how this barrel continued to shoot acceptably even with an eroded throat. Eventually even that end grew unacceptable too. Thus as this example illustrates a properly lapped barrel ....with a taper toward the the muzzle will shoot acceptably even after the throat erodes. if you can seat bullets further and further out and "chase the throat" whilst upping your load a fella can get a few more miles out of a good barrel. Some barrels just quit shooting acceptably in a couple thousand rounds. And the benchrest boys change out barrels about every 1500...just in case. I used to buy their take offs for my varmint rifles for cheap ($50) ....they shot great for quite a while (I never kept track of them for they were truly abused)
Jerry G
Uber Master Poster
Uber Master Poster
Posts: 2746
Joined: Wed Apr 12, 2006 2:34 pm
Location: Casa Grande, AZ

Re: Barrel life, Bob's 7x08's and other's experience

Post by Jerry G »

I have never seen bbl life expressed as seconds in the bbl. I think that makes a little sense. I also think burn rate has something to do with it. The hotter the fire at the case mouth, the more erosion you will have there. Heat is your enemy.
User avatar
Another Dang 9
Master Poster
Master Poster
Posts: 1333
Joined: Thu Dec 10, 2009 7:24 pm
Location: The Peoples Republic of Massachusetts

Re: Barrel life, Bob's 7x08's and other's experience

Post by Another Dang 9 »

A poor muzzle crown will do more damage to accuracy than throat erosion. Its the last thing the bullet sees before it exits the barrel that matters most.
Its a dog eat dog world and I'm wearing milk bone underwear.
NRA Endowment Member
jask
A Poster
A Poster
Posts: 133
Joined: Tue Oct 29, 2013 4:56 am
Location: San Diego, California

Re: Barrel life, Bob's 7x08's and other's experience

Post by jask »

I have only shot out one barrel, a short 308 cartridge using about 39 grains of 4064. I shortened the chamber early on and got about 5k rounds through it. I remember checking the throat and found a few rectangle chunks missing in the first 1/2 inch. It went from that to absolutely dying in two matches. I was missing by feet on the rams. Got it home and scoped it again. About 5 inches of rifling was totally gone. I have about 3k rounds in my factory 7.08 hunter and the throat still looks good.
ywltzucanrknrl
A Poster
A Poster
Posts: 203
Joined: Thu Aug 06, 2009 3:41 pm

Re: Barrel life, Bob's 7x08's and other's experience

Post by ywltzucanrknrl »

Thanks Bob---I would say OCD---but I've come to believe it's a good idea to keep a round count---for one thing, if you don't it's very hard to estimate, as I've found out.
Topclass, interesting on the barrel time idea. Kind of wonder though and how would you answer this? With that idea in mind, it would intuitively lead to slower velocity bullets wearing out the barrel faster than fast velocity bullets---slower bullets would equal longer barrel time. I've always thought that higher velocity heavier/longer bullets were the worst culprit.
Anyway, thanks everyone, by the way, I'm in agreement with the muzzle---certainly better to have a bad throat than a bad muzzle.
thauglor
AAA Poster
AAA Poster
Posts: 628
Joined: Thu Aug 08, 2013 9:18 pm

Re: Barrel life, Bob's 7x08's and other's experience

Post by thauglor »

ywltzucanrknrl wrote:Thanks Bob---I would say OCD---but I've come to believe it's a good idea to keep a round count---for one thing, if you don't it's very hard to estimate, as I've found out.
Topclass, interesting on the barrel time idea. Kind of wonder though and how would you answer this? With that idea in mind, it would intuitively lead to slower velocity bullets wearing out the barrel faster than fast velocity bullets---slower bullets would equal longer barrel time. I've always thought that higher velocity heavier/longer bullets were the worst culprit.
Anyway, thanks everyone, by the way, I'm in agreement with the muzzle---certainly better to have a bad throat than a bad muzzle.
I think the number of seconds of life is a very inaccurate way to estimate useful barrel life; you can calculate it after the fact but not use it to estimate life. Your intuition is correct. All evidence points to the faster a bullet the worse the wear.
User avatar
Another Dang 9
Master Poster
Master Poster
Posts: 1333
Joined: Thu Dec 10, 2009 7:24 pm
Location: The Peoples Republic of Massachusetts

Re: Barrel life, Bob's 7x08's and other's experience

Post by Another Dang 9 »

All evidence points to the faster a bullet the worse the wear.[/quote]

Bullet speed is a consequence of powder capacity which affects speed. Copper is soft so barrel damage due to bullet speed is minimal. It's the hot flame of the powder that is the culprit of throat erosion. As the articles Bob has posted state.
Its a dog eat dog world and I'm wearing milk bone underwear.
NRA Endowment Member
thauglor
AAA Poster
AAA Poster
Posts: 628
Joined: Thu Aug 08, 2013 9:18 pm

Re: Barrel life, Bob's 7x08's and other's experience

Post by thauglor »

What AD9 said :mrgreen:
Bob Mc Alice
Expert Master Poster
Expert Master Poster
Posts: 1772
Joined: Mon Sep 11, 2006 6:54 am
Location: Colorado

Re: Barrel life, Bob's 7x08's and other's experience

Post by Bob Mc Alice »

I will say one thing about visible wear using a Hawkeye borescope. That alligator skin appearance talked about in the articles is MUCH less evident in a stainless steel barrel vs. a carbon barrel with the same quantity of shots fired. Don't get me wrong, there is still steel vaporizing with each trigger pull, just not as severe looking as carbon steel. The origins of stainless steel for rifle barrels began nearly a century ago from our military looking for superior alloys to increase machine gun barrel life.
Snake
AAA Poster
AAA Poster
Posts: 863
Joined: Wed Jul 07, 2010 12:37 pm
Location: St. Louis, Missouri

Re: Barrel life, Bob's 7x08's and other's experience

Post by Snake »

bob.....stainless steel is a version of carbon steel with a higher nickel content Chrome molybdenum is the primary characteristic of non stainless barrels. Gas checking or alligator skin develops in both from heat and thus repeated sudden expansion and contraction of the surfaces. No doubt stainless is harder and has various wear advantages...such as requiring less care. But chrome moly generally breaks in faster because the surfaces burnishes quicker. Lapping is easier and quicker because tool marks are more easily lapped out. Of course bluing is required to preserve the exterior of chrome moly (hence it requires more attention and care) But chrome moly is cheaper, and its accuracy potential is historically established. However cryo tempering stainless barrels improves their machinability, life, and accuracy potential / precision..
That said stainless is preferred because of its care advantages and popularity, Stainless was invented by Pierre Berthier in France in 1821. It was first patented by the English in the 1870s. The first US patent was in 1929....there are a bunch of stainless alloys generally listed as 100, 200, and 300 series......rifle barrels are 300 series ;)
Bob Mc Alice
Expert Master Poster
Expert Master Poster
Posts: 1772
Joined: Mon Sep 11, 2006 6:54 am
Location: Colorado

Re: Barrel life, Bob's 7x08's and other's experience

Post by Bob Mc Alice »

Dearest Snake, as you may have forgotten, I am a retired damn fine machinist. I have machined every alloy of SS you can think of and some you have not even heard of. I know the properties and chemical make up of most metals. :-B
Post Reply