Barrel Life Question

[Sky Dog]

I keep hearing about the advancement of long range accuracy with the .260, 6mm and 6.5 mm. When does muzzle velocity come into play. I've heard a .264 Win Mag is very hard on barrels.
Not so much on Weatherby Mags, .300 Win Mags or 7mm Rem Mags. I realize quality of steel is a factor. What's the most bang for the buck?

 

[Varminterror]

If you have not heard barrel life is poor on Weatherby mags or 7RM, you have had your fingers in your ears. Most guys shooting these don’t complain as much as 22 cal to 6.5mm shooters, because these big case cartridges are generally hunting rifles, where round counts are low by nature, and ammo cost drastically outweighs barrel costs (even more so than the smaller bores, see below).

Barrel life and cartridge performance are always a trade off. The most “bang for your buck” is generally going to be a rather poor ballistic performer compared to the hotrod cartridges in its field. For example, a fast twist 243win can have half of the wind drift and less drop - with considerably less recoil - than the same case in 308win, but a 308win barrel will last 3000-5000rnds, where a 243win barrel will last 800-1800rnds.

You have to first consider the application - if 1,000yrd wind drift doesn’t matter in your application, you can get away with a cartridge with a lesser overbore ratio.

One other thing to consider - the expense in burning out barrels is rarely about the cost of the barrel themselves. If you’re shooting 2,000rnds per year of .243win or 308win you likely spent around $1500 on ammo (spitballing 2 boxes primers at $30 each = $60, 8lb powder at $250, 500 brass at $1/ea = $500, 35c/bullet x 2000bullets = $700, plus targets, range fees, gas, brownie-point presents for the wife, and whatever else you may have spent). So buying a $350 barrel and spending $250-300 per year instead of every other year really isn’t a huge difference. What MAY be a difference is the fact you’re getting 6mm bullets for 35-40cents each, vs. 45-55 cents each. A dime more per bullet yields $200 per year, a third of the barrel & install cost.

For some applications, spotting your misses and impacts matters, so extra recoil is an extreme disadvantage. Less wind drift might be a huge advantage to your score at some matches as well - so consider wasted fees and competition travel because of cartridge induced misses to be a soft, yet real cost in this equation as well.

So in general, I consider it silly when some newbie talks about buying some sub-optimal cartridge to start out in long range shooting, pretending they’re saving a bunch of money by buying barrels half as often. For hunting, a low volume game, a barrel will last a lifetime, so again, the consideration of barrel life is largely moot.

 

[Varminterror]

To add: quality of steel is rarely of any significant contribution to barrel life. Coatings, linings, and steel selection have minute influences upon barrel life. Cartridge choice rules the game. If one barrel material type held accuracy significantly longer than another, ALL competition formats would use THAT type. But we don’t. You’ll see chromoly and stainless barrels side by side at any match.

 

[Llama Bob]

It depends a huge amount when you consider a barrel to be shot out. Most hunting small bores will start showing some accuracy degradation between 1000 and 2000 shots depending. But they may not fall below acceptable hunting accuracy for thousands of shots after that. So it depends on what your standards are.

 

[Llama Bob]

To add: quality of steel is rarely of any significant contribution to barrel life. Coatings, linings, and steel selection have minute influences upon barrel life. Cartridge choice rules the game. If one barrel material type held accuracy significantly longer than another, ALL competition formats would use THAT type. But we don’t. You’ll see chromoly and stainless barrels side by side at any match.

The difference between 4140 and 416 is small, but the difference for some coatings can be huge. Hard chrome and ferritic nitrocarburization will often double or more the life of a barrel

 

[Varminterror]

The difference between 4140 and 416 is small, but the difference for some coatings can be huge. Hard chrome and ferritic nitrocarburization will often double or more the life of a barrel

It depends on what you consider to define the barrel life. If opening groups by 50% is the scope, or opening to inssuficiently accurate for the competition, I haven’t seen nitride or chromies to be hugely better in barrel life.

If blasting targets is the game, and not doubling from 2MOA to 4moa is the scope. Sure.

 

[Llama Bob]

It depends on what you consider to define the barrel life. If opening groups by 50% is the scope, or opening to inssuficiently accurate for the competition, I haven’t seen nitride or chromies to be hugely better in barrel life.

The spec for the hard chrome on the FN SPR is 1MOA at 10,000 rounds. I'd say that's significant.

 

[denton]

Several years back, Browning published test data comparing their chrome lined 22-250 barrel to an unlined barrel. Both barrels held essentially the same accuracy for the initial part of the test. As round count increased, eventually both barrels hit a "knee" in the curve, past which group size increased exponentially. The knee of the chrome lined barrel was at about twice the round count of the standard barrel. IIRC, 1500 for the standard barrel vs. 3000 for the chrome lined.

 

[Jim Watson]

1 MOA is so 20th century.

 

[Riomouse911]

As was stated, all large-capacity magnum cartridges pour a LOT of powder gasses down the bores when they're fired, and heat/friction etc. wears out a barrel quickly. All magnum rounds are tough on a barrel no matter who makes them. And as was also stated, volume of fire adds to it. Lots of bullets fired through a bore rapidly will erode the barrel faster than slow shots allowing the barrel to cool between them. (High-volume varmint shooters claim have this problem...I've never had the luck to be on such a non-stop shooting expedition though.)

My Weatherby Mark V .300 rifle is over 45 years old, but the bore looks brand new because it's been fired so little and only a few at a time. A couple of my newer AR barrels are nearing their end due to rapid fire and a much, much higher volume of fire down the pipe per shooting session.

Stay safe!

 

[Llama Bob]

Several years back, Browning published test data comparing their chrome lined 22-250 barrel to an unlined barrel. Both barrels held essentially the same accuracy for the initial part of the test. As round count increased, eventually both barrels hit a "knee" in the curve, past which group size increased exponentially. The knee of the chrome lined barrel was at about twice the round count of the standard barrel. IIRC, 1500 for the standard barrel vs. 3000 for the chrome lined.

FWIW, supposedly during the FBI acceptance test for the FN SPR they shot 15,000 rounds with no change in (~0.5MOA) accuracy, which wildly exceeded the spec 10,000/1MOA spec. I don't have any first hand knowledge if this is true or not, but they use a pretty thick coat of chrome so I wouldn't be that surprised.

 

[Jim Watson]

There was a legend that they used M240 machine gun barrels as barrel blanks for the SPR. Truth or fiction, I don't know.

 

[Llama Bob]

I think there's at least a grain of truth to it, because the thick chrome coatings were pioneered for machine guns. And you'd need an oversize blank to accommodate the thicker coating and still end up at .308/.300. So it really wouldn't surprise me if the the blanks were the same. I suspect the SPR needed a lapping step the 240 probably didn't get though.

 

[denton]

When I was doing consulting work for Lake City, they generally retired 5.56 M16 barrels at 10,000 rounds.

 

[Dibbs]

I look at it like this. My 1 and 2 MOA performers will never see enough rounds thru their barrels to degrade their performance in my lifetime.

Folks plowing through enough rounds to wear out their barrels are already spending so much on ammo
that the cost of a replacement barrel should be negligible.

When you go 500,000 miles in a car, are you upset when you need to replace the engine?

 

[Jessesky]

I don’t know who told you Weatherby mags are not hard on barrels, if Weatherby has a middle name, I’d guess it’s spelt “overbore”.


But yes, a 264win mag is a good example of one of the fastest barrel burners out there.

There’s a few things to consider, one being the expansion ratio and surface area, this is why small overbore catriges burn barrels. There is a large amount of powder being shared over less steel (the surface area) in a sense. Another common thought is the velocity of the cartridge, but I believe this to me a misconception associated with hot loads. In handloads what really burns barrels is heavy bullet weights in max loads. The heavy bullet weight, because of the greater mass and intertia, takes longer to jump to the lands and the grooves. This increases the amount of time the throat is exposed to the heat and pressure. I do not have the tools to test this, but this is what I have read from the people who do have the tools, and it makes sense to me.

 

[Ks5shooter]

Pick you caliber,shoot as often as you like. Enjoy the firearm replace barrel if needed. No sense in buying a firearm and worrying about round count until accuracy starts to suffer. If you don't enjoy shooting it whoever gets it when your gone will

 

[jmr40]

The more powder you burn combined with a smaller bore means shorter barrel life. It's not exactly related to speed, but more powder means more speed. It is the heat generated that does the damage. The 6mm's have been known for shorter barrel life than say 308 which uses similar powder charges in a larger bore. It varies a lot, but most target shooters expect a 308 barrel to last about 5000 rounds before accuracy starts to deteriorate. For accuracy acceptable for most recreational shooters or hunters double that.

I've heard of some 6mm/243 barrels being shot out at 1000 rounds. The fast 6.5's such as the 264 WM are about the same. The current crop of 6.5's such as the 6.5CM and 260 are supposed to be unacceptable at about the 2000-3000 round mark, but once again for most peoples uses probably double that. The old 6.5X55 was not traditionally loaded hot so it should be in about the same class as the 260 or 6.5 CM but I've never seen any data on it.

 

[Varminterror]

No sense in buying a firearm and worrying about round count until accuracy starts to suffer.

Start worrying before accuracy falls off - you need to have the new barrel on order a couple months before the old one burns out, and have a smith lined up with you ready in the queue, otherwise you might be sitting on a burned out rifle with nowhere to go for a few months, to over a year. For example, Bartlein is 4-6mos right now, and GA Precision is ~3 months to do the install. You might find the barrel you want in someone’s inventory, but you also might not.

I've heard of some 6mm/243 barrels being shot out at 1000 rounds.

My Rock Creek 6 Creedmoor barrel dropped 120fps under 500rnds this season (n=1 experience, I would not use them again because of this). It lost ~225fps and doubled group size by 1200. Every 100rnd match day I shoot was losing more and more speed from about 800 on, and the nodes are creeping all over. I’m beating a dead horse with the barrel at this point, at 1400rnds. New barrel waiting on the shelf until after deer season this week. Way more accurate than needed for killing deer, but on the edge of unacceptable for the competition I shoot - which isn’t nearly as demanding of precision as benchrest or F class. I shot a 6.5 creed half of my season this year, and didn’t get to nearly as many matches as I had planned due to work, but those 1200rnds completely finished my barrel in 6months.

 

[otisrush]

I bought my first (and only) .243 2 years ago. (Use is target shooting only......not high precision/competition.....but I enjoy high power steel silhouette and experimenting with loads in an effort to optimize group sizes.) I think I learned of the .243's propensity to burn out barrels pretty quickly after I'd ordered the gun but prior to taking delivery. I wondered if I'd made a mistake with that caliber choice: Although I'm a lifelong shooter I've never shot out a barrel and hadn't internalized (as I do now) how barrels are a consumable.....kind of like ammo.

That gun has ~1,400 rounds through it and is exhibiting signs of it throwing in the towel. I haven't tracked velocities that closely. A 70gr Sierra load that used to be wonderful now looks like a shotgun. It's still shooting 105gr and 115gr bullets well. My smith put his bore scope down it and his first word was "Wow!". The first 5" or so of the rifling is charred and cracked. But I'm actually *happy* it's about to go: I'm going to rebarrel in 6.5CM and have the action blueprinted. New barrel is on order (not sure when it will arrive) so it's in the basement when the current one is totally gone. (Per @Varminterror 's comments). The rebarrel will open up a whole 'nother world and I'll basically be getting a new gun. It almost feels like reloading from the standpoint I'm not tossing everything but rather improving and re-using and making something better.

"Bang for the buck" is highly subjective - based both on use (e.g. hunting, varmint, target) as well as budget. I'm retired and shooting (which includes reloading) is my most favorite way to spend my time....and this part of my rifle repertoire is my favorite segment of shooting right now. So I look upon barrel replacement as fun and exciting....because it'll take me into new adventures.

 

[taliv]

Keep in mind the wear is in the throat not the bore. The implication is that if the blank is chromed or otherwise treated and then the chamber is cut, you’ve basically accomplished nothing.
If the chamber is cut and then chromed / treated, then it might be interesting to track the data.

 

[Jim Watson]

Old gunzine article alert.

Way more accurate than needed for killing deer, but on the edge of unacceptable for the competition I shoot

A target shooter wrote that all his friends had .30 hunting rifle barrels better than stock, even though they were takeoffs from his target rifles. Shortening from the breech, rethreading for other actions, and rechambering got them clean throats.

But then there was the guy who could not find a barrel (and load) accurate enough for the job. Then his gunsmith put a dial indicator on his rear sight and found a wee bit of slop in the adjustments. Untold time and money spent looking in the wrong direction.

 

[Nature Boy]

Start worrying before accuracy falls off - you need to have the new barrel on order a couple months before the old one burns out, and have a smith lined up with you ready in the queue, otherwise you might be sitting on a burned out rifle with nowhere to go for a few months, to over a year

When I had my 6mm BRA built this year I included 2 barrels and had the smith go ahead and chamber the 2nd one, for the very reason you mentioned above

 

[Varminterror]

When I had my 6mm BRA built this year I included 2 barrels and had the smith go ahead and chamber the 2nd one, for the very reason you mentioned above

Yup. Kinda sucks, but it is what it is. I started doing that a couple years ago - buy two barrels up front and have the Smith note the tenon specs for headspace. Order the 3rd barrel when the 1st goes down, install the second, and have the 3rd in hand before the 2nd burns out.

 

[Elkins45]

You can make a barrel chambered for an overbored cartridge last significantly longer if you don’t let it overheat. A barrel that’s already hot is less resistant to erosion from a quick succession of shots.

My most overbore rifle is a 257 Weatherby that I put together in the early 90s. It’s strictly a hunting rifle so it’s at about 500 rounds now. I suspect it will outlive me unless I win the lottery and go on a serious hunting spree.