View Full Version : Barrel Wear/Replacement
July 15, 2009, 05:34 PM
I am pretty new to long range shooting and am planning on putting a new rifle/scope combo together.
I have a question about Barrel wear/replacement. How long does a typical barrel last (maybe in a 308win or 300 win mag)? Also, can you typically replace the barrel on a tactical long range rifle?
I would also like to use this weapon to hunt deer/elk. I was thinking about getting one of the Savage or remington rifles. Do they have replaceable barrels? I am looking to keep the rifle under $1000 so I can get a good scope.
I know these are some "loaded" questions.
July 15, 2009, 06:11 PM
So much is going to depend on the loads you use, the powder, and how hot they are. Before the bore wears down, the throat is going to erode. On some hyper velocity wildcats, you can only shoot a few thousand rounds before throat erosion starts affecting accuracy. On a 308 loaded to factory levels, 10K rounds should not be a problem.
July 15, 2009, 07:48 PM
All common mass produced guns I am aware are capable of being rebarreled (unless there are some oddballs floating around somewhere.) And the definition of being worn out varies depending on the shooter. For one guy it might be when the groups open up to 2 moa, the next might consider a barrel whose groups open up 1/8" to be toast, etc. Really serious benchrest guys might replace their barrel every year whether it really is "worn" or not. My general rule of thumb is when I can start noticing the groups consistently getting larger without having to measure them it's probably time to get a new pipe.
The .300 win mag will have substantially lower life expectancy than a .308. A .300 barrel will last in the ballpark of somewhere between 1500 and 2500 rounds before accuracy is degrading noticeably. Many target guys claim to get 5000-8000 out of a .308 before having to rebarrel (real competitive guys with hot handloads maybe closer to 3000 and 10000+ is not unheard of for the average joe). Of course these depend on some factors. For example, rapid fire shooting with a super hot barrel or shooting near max loads are going to wear it out faster. In the end, a rebarrel is a only a few hundred dollars (more if you get very high quality barrels), so I would not really worry about wearing out barrels.
Also, as a bit of advice from someone whose been there, if you have not shot a .300 win mag, make sure you go to the range and shoot a box before you settle on it as a caliber of choice for target work. It's a great round, but recoil can be punishing, especially in a tactical weight rifle.
July 15, 2009, 10:31 PM
The Savage barrel is user replaceable with affordable tools.
Remingtons, Winchesters, and others should go to a knowledgeable gunsmith especially if you are expecting a lot of tackytickle performance.
July 18, 2009, 01:58 AM
AFAIK, the only commercial gun you cannot have a barrel changed on by your local gunsmith is the Browing A-bolt. The factory uses some kind of industrial super Loctite on the barrel threads that impedes its removal, and they say you need to return it to factory service for a new barrel. No idea why they did that?
Barrel life depends on conditions. About ten years ago, Sierra ballistics technician Kevin Thomas did an experiment shooting out stainless .308 barrels on Remington actions by using them in the company's normal QC testing process. Sierra keeps aside a special lot of 168 grain MatchKings that turned out to be more accurate than their normal production, and that they use as reference bullets in testing. He fired those in the six barrels he shot out while looking to see if cryo-treating or moly-coating did anything to extend barrel life? In the process he found the untreated barrels with untreated bullets went about 3500 rounds before he could detect beginning signs of the barrel being shot out. IIRC, Cryo-treating added 14%, (4000 rounds total), which is close to the roughly 20% it is credited with for extending the wear life of stainless tooling. Cryo-treating chrome-moly tool steel is usually claimed to double its wear resistance, and I am sorry Thomas didn't test some chrome-moly barrels to see if the matter applied there, as well. About 3000 rounds barrel life is what you hear service rifle match shooters talk about for .308.
I don't know if you've ever shot a barrel out, but the initial signs can disguise themselves pretty well. It comes in the form of a flyer you can't account for. Those just become more and more frequent until, about the time you are getting one every tenth shot, it finally dawns on you that the problem isn't you. When I shot out my first M1A barrel it happened like that. The fliers were a little over an moa off POA, so called X's instead scored 9's in slow fire. I would say it progressed from being one every 50 shots to one every 10 shot over a span of a couple or three hundred rounds. So you can see how shooters would blame themselves for errors that size until the frequency became great.
We have a competitive shooter on another forum who is a former Aberdeen Proving Grounds employee who conducted gun testing, among other things. He has a theory that hardened carbon residue is a wear factor and makes a good argument for it. He found barrels that shot out in a few thousand rounds in semi-auto fire could, contrary to intuition, go 15,000 or more when fired full auto, which keeps the non-metallic fouling warm and soft. The hammer forged 5R grade steel barrels Remington buys for the M24 sniper system have been reported to go 20,000 rounds, but the snipers clean more often than match competitors. Also, as mentioned above, the steel matters, and I don't know how the metallurgy of that steel compares to other barrel steels. It could be a significant contributor.
August 27, 2009, 06:04 PM
There are numerous variables in determining if/when a barrel needs replacement. For instance, those who shoot F_CLass or benchrest have significantly greater need for precision accuracy and repeatability. Hunters need only be able to hit the engine room from their maximum comfortable distance... quite a bit of lattitide. A barrel considered "worn out" by a benchrest shooter will still have thousands of hunting rounds worth of life left in it.
There are more objective means of predicting accurate life and one of these is known as the overbore index. Basically, the case capacity in grains of H20 divided by the surface area of the case mouth opening.
for instance... the 300WM has a case capacity of 84 grains of water
divided by the 308 cal. opening surface area (.07450") = 1127
That number is a relative index...
Numbers under 800 have excellent barrel life measured in thousands of rounds.
Numbers above 1100 are brutal, with accurate life being 1500 or less, The 6.5X284 has an OBI of 1205 and it is well known for going through barrels in as little as 800 - 1000 rounds.
September 13, 2009, 09:33 PM
Barrel life's a relative thing as several posts have mentioned. Unclenick's reference to Sierra Bullet's tests pretty much duplicate what Sierra's former head ballistician, Martin Hull, told me back in the 1960's. He rebarreled their rail guns used to test bullets for accuracy at about 3000 rounds. There's a formula that predicts that I'll cover later. Top highpower match rifle shooters would rebarrel their. .308 Win.'s at about 3000 rounds, but didn't want to go to the Nationals with more than 1500 rounds through one. Their 30 caliber magnums (.30-.338, .300 Win. Mag., etc) barrels would last about 1200 rounds. I had a tack driving .264 Win. Mag. in the late 1960's that lasted 640 rounds before it went from 2/3rds to 2 MOA at 600 yards in three shots.
Regarding those "reference" bullets Unclenick mentioned Sierra uses to test their barrels with really are super accurate. Sierra used to call them "standards" and the best of their 30 caliber ones would shoot in the ones and sometimes the zeros; one 10-shot group after another. When located in California, Sierra used to sell these "standards" in plain brown boxes with 1000 bullets in each one. They still had the sizing lanolin on them and weren't polished bright and shiny; that's how they're tested. These were taken right out of the pointing machine as a hand full were grabbed and seated in pre-prepped charged cases for testing. As long as the test groups were under 2/10ths inch, a special barrel would catch them, then they'd be packaged and taken to big highpower rifle matches to sell to competitors. Accuracy wise, they shot 1/3rd better than the bullets sold in green boxes. These bullets were the ones used to win most of the highpower matches and set most of the records until they quit selling them when they moved their plant to Missouri. I've still got some of those 30 caliber 168, 180, 190 and 200 grain "standards."
A formula I've used for years to calculate barrel life is as follows: 1 grain of powder for each square millimeter of the bore's cross sectional area will result in about 3000 round of accurate life for that cartridge. I think "bore capacity" is also the same thing; a 30 caliber barrel has a bore capacity of about 45 grains. So, a .308 Win. with about 45 grains of powder will get 3000 rounds of accurate barrel life. Double the charge weight for a given bore diameter (twice bore capacity) and you'll get 1/4th the barrel life; a 30 caliber magnum burning 90 grains of powder will get only 750 rounds of most accurate barrel life. So far, this has worked well for competition. Double the number for hunting accuracy and quadruple it for service rifle combat accuracy.
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