Barrel Life

[Randy Bo]

I was reading about the early testing of the Army’s M24 sniper rifle when I ran across this:

“The actual rifle requirements for accuracy were .35 MOA from a machine rest and according to Major John Mende (ret.) this accuracy had to be maintained to 10,000 rounds. He stated, “Interesting side note was there was a 10,000 round requirement for the barrel to maintain the original accuracy. In fact after some 10,000 round tests we discovered the accuracy improved. A few barrels were tested past 20,000 and accuracy never went below the original accuracy requirement.”

Shortly after reading this article, I read some random articles on barrel life and the conclusions were all over the place. Some guys state a 6.5 Creedmoor barrel shoots-out at 1200 rounds and then some guys state that for calibers like the 6.5 or 308, 5000 rounds is more realistic.

Personally, I have never shot any of my guns enough to shoot a barrel out.
So, any thoughts or experiences would be appreciated.

 

[Phil Giordano]

To me, barrel life depends more on "how" you shot than "how many". If you take time between groups, let cool the barrel well, and clean deeply the barrel every 30/40 shots, a barrel can really last for very long I guess. Also a good break in seems to prolong barrel life. A factor that "burns" the barrel quickly is the type of powder, a very slow powder in fact (producing more heat) seems to erode the rifling faster than a quick one. Me, I have shot a lot with a 300 Winch and a 300 Wby and I yet have to see any effect on groups - I believe "cooling" & "cleaning" are key factors, more than numbers of rounds.

 

[mark-hunter]

Do you have some link of this source?

I remember reading (a long time ago) and cannot find this source again, so maybe I am getting it all wrong, that accuracy requirement for army sniper is 2 MOA with standard FMJ ammunition used for machineguns. (those are most commonly available on battle field, and for this reason used as measuring stick).
Then, better accuracy would be expected with specialised ammo of some hpbt type, but never did I hear of 0,35 moa.

 

[colorado]

I have a BDL in 270 Win I bought in the late 60s. I have over 5000 rounds through it and it still shoots nickel sized groups at 100 yards. Awesome rifle. I clean my rifles after each time at the range or at the end of a hunting trip, but I'm not OCD about it. I believe over cleaning harms more bores than shooting them a lot. Just my conjecture though.

 

[Phil Giordano]

I have a BDL in 270 Win I bought in the late 60s. I have over 5000 rounds through it and it still shoots nickel sized groups at 100 yards. Awesome rifle. I clean my rifles after each time at the range or at the end of a hunting trip, but I'm not OCD about it. I believe over cleaning harms more bores than shooting them a lot. Just my conjecture though.

Totally agree on damages caused by over cleaning, too...

 

[Randy Bo]

Do you have some link of this source?

I remember reading (a long time ago) and cannot find this source again, so maybe I am getting it all wrong, that accuracy requirement for army sniper is 2 MOA with standard FMJ ammunition used for machineguns. (those are most commonly available on battle field, and for this reason used as measuring stick).
Then, better accuracy would be expected with specialised ammo of some hpbt type, but never did I hear of 0,35 moa.

U.S. ARMY M24 SWS

The M24 brought the US Army into the modern bolt action sniper rifle game in the late 1980s, and it was a gem

www.snipercentral.com

 

[40inarow]

I was reading about the early testing of the Army’s M24 sniper rifle when I ran across this:

“The actual rifle requirements for accuracy were .35 MOA from a machine rest and according to Major John Mende (ret.) this accuracy had to be maintained to 10,000 rounds. He stated, “Interesting side note was there was a 10,000 round requirement for the barrel to maintain the original accuracy. In fact after some 10,000 round tests we discovered the accuracy improved. A few barrels were tested past 20,000 and accuracy never went below the original accuracy requirement.”

Shortly after reading this article, I read some random articles on barrel life and the conclusions were all over the place. Some guys state a 6.5 Creedmoor barrel shoots-out at 1200 rounds and then some guys state that for calibers like the 6.5 or 308, 5000 rounds is more realistic.

Personally, I have never shot any of my guns enough to shoot a barrel out.
So, any thoughts or experiences would be appreciated.

I have shot Rifle Silhouette going on 35 years now. I have shot out 2 barrels, a 7-08 at 6600 rounds and a 6.5-08 (260 Rem) at 7300 rounds. I clean using JB Bore paste and Kroil using patches on a jag and no brushes. I believe a lot of wear comes from brushes banging on the chamber. I learned this method from benchrest shooters. Kroil is an outstanding penetrating oil and the JB paste is harder than copper but softer then steel. So the Kroil loosens the copper fouling and the JB cleans it out. I believe I get longer barrel life using this method. Accuracy is maintained. I also used moly coated bullets exclusively. Moly coating will extend your high accuracy shooting life of your barrel. Once you learn how to do it, it's easy.

 

[Randy Bo]

I have shot Rifle Silhouette going on 35 years now. I have shot out 2 barrels, a 7-08 at 6600 rounds and a 6.5-08 (260 Rem) at 7300 rounds. I clean using JB Bore paste and Kroil using patches on a jag and no brushes. I believe a lot of wear comes from brushes banging on the chamber. I learned this method from benchrest shooters. Kroil is an outstanding penetrating oil and the JB paste is harder than copper but softer then steel. So the Kroil loosens the copper fouling and the JB cleans it out. I believe I get longer barrel life using this method. Accuracy is maintained. I also used moly coated bullets exclusively. Moly coating will extend your high accuracy shooting life of your barrel. Once you learn how to do it, it's easy.

40inarow
Did you ever experience a brief improvement in accuracy from the midpoint to the end of a barrel’s life?

 

[GuttormG]

6,5x55 as used in competetive shooting within norwegian rifle associatio , a barrel will hold good enough accuracy for +/-5000 rounds. Same shooting, same gun set-up but a 308win barrel will be ok up to 10-12000 rounds.
Range is 200meters an "center-x" is 50mm in diameter. 35 shots in 12 min.

Very few of this shooters spend much time on advanced cleaning, it do not makeba difference.

 

[BeeMaa]

I've seen several military rifle barrels ruined long before their time due to improper cleaning from not using a bore guide, improper use of solvents, over scrubbing, dings in the throat & crown... It comes down to technique when cleaning. Getting it right the first time is important. That usually means moving in a slow & deliberate manner and having an understanding of what you are doing & why. Hard to teach that to young service members most of the time.

As for barrel life and contributing factors (as others have said)...bullet speed and shooting a "hot" barrel would be the major factors.

I'm a hunter and have yet to shoot beyond 5K rounds through a single barrel. Possible exception of an old 22lr that's long gone, but it was still accurate when I sold it. Wife and I do a lot of dry fire practice so that keeps the round count down. I also clean after each range session, but it's little more than a bore snake with some CLP on it most of the time. No change in accuracy but like I said, I'm a hunter not a benchrest shooter. If I were on the bench, my methods would be much different...probably closer to what @40inarow is doing.

 

[Hunter-Habib]

During the India Pakistan War in 1971, I observed several Lee Enfield in .303 British which had very badly worn rifling in them. The rifles were at least 26 years old at the time (being brought into the country during the British Colonial Era) and were used with 174Gr cordite loaded berdan primed FMJ military military ball. Which is what probably accelerated the bore wear.

The .220 Swift and the 7mm Remington Ultra Mag are two calibers which are notorious for having short barrel lives.

I do know that Harry Selby shot his .416 Rigby Mauser enough to necessitate sending the rifle back to John Rigby & Co. for a rebarreling job.

 

[Firebird]

I have only ever shot out one barrel. A 7mm stw-so slow burning powder loaded to its max. I had over 2000 (thats a Guess)rounds through it which included too much load work up trying to use newer, supposedly better bullets. I figure I fired a couple hundred rounds at the range for every round I spent at an animal.

 

[40inarow]

40inarow
Did you ever experience a brief improvement in accuracy from the midpoint to the end of a barrel’s life?

No I haven't. I use Shilen stainless steel barrels and match bullets. The accuracy holds but when they go downhill they go fast.

 

[lockingblock]

The M24 is barely a 1MOA rifle on a good day, using military ammo.

I’ve seen it numerous times.

 

[browningbbr]

To me, barrel life depends more on "how" you shot than "how many". If you take time between groups, let cool the barrel well, and clean deeply the barrel every 30/40 shots, a barrel can really last for very long I guess. Also a good break in seems to prolong barrel life. A factor that "burns" the barrel quickly is the type of powder, a very slow powder in fact (producing more heat) seems to erode the rifling faster than a quick one. Me, I have shot a lot with a 300 Winch and a 300 Wby and I yet have to see any effect on groups - I believe "cooling" & "cleaning" are key factors, more than numbers of rounds.

Just to emphasize the impact of cleaning mentioned by Phil G.: Several times, I have had members of my sportsman's club complain to me that the barrel was "shot out" of their hunting rifle. In almost every case, a vigorous and prolonged scrubbing with a good copper solvent completely remedied the problem.

I'm not saying the cleaning is the only factor, but it's a big one.

 

[Tom Leoni]

There are some objective factors that affect barrel life. The principal one is heat, specifically at the throat. The hotter a barrel is allowed to become at that particular point, the shorter the barrel life. This is why many military rifles that have been put through intense shooting sessions have a "shot out" barrel--90% of the times meaning a "corroded" throat. Rule N. 1: let your barrel cool down between shots if you want to extend your barrel life.

One of the factors that contributes to barrel wear is the angle of the cartridge's shoulder, which is why some of the latest 6.5 Whizbangs are getting a dubious reputation as barrel-burners. According to the well-known Venturi principle, a build-up of pressure before a sharp constriction results in a commensurate increase in velocity on the other side. Thus the lava-hot un- or partially-burned powder-grains of (say) a 6.5 Creedmor will shoot out of the case mouth like so many accelerated particles and affect the throat to some degree. Here's where the previous rule applies: allow a barrel to become incandescent-hot, and the molecular composition of (especially) the throat will go to the proverbial dogs; let it cool down between shots, and even a 6.5 Creedmor will give you an excellent barrel life.

P.S.: given the above, it's clear what partial advantage straight walled cartridges--as well as cartridges with minimal shoulder angles--have. Pressures and velocity/acceleration are constant throughout ignition and there will not be nearly as much stress in the throat. Naturally, with the tricks I've described, even this becomes largely academic.

 

[lockingblock]

To add to the above…Barrel life is relative to the purpose. High velocity calibers in small diameter bores will consume barrels faster than the opposite. Your accuracy standards may allow longer life than a match shooter that needs .3 MOA to be competitive.

Generally, 300 win mag with heavies (220 SMK), will be more or less done around 1k rounds. 308 can go 10k…but not really if you are looking at the throat and watching how it is damaging the bullets due to roughness. If you only look at 100yard groups, it looks great…but the rough bore creates BC variables on the bullet that causes dispersion at distance.


5.56 is relative to the rifle. The gas port often goes before the throat on an AR. 10 inch guns die around 5-7k while 14 inch guns die about 8-10k and 20 inch guns will go until there is no rifling in the bore.

it’s a complex topic with multiple variables. Overbore is real…

 

[Randy Bo]

A

The M24 is barely a 1MOA rifle on a good day, using military ammo.

I’ve seen it numerous times.

According to Wikipedia the accuracy test utilized a “Government Approved Machine Rest”.
The testing procedure is covered in “MIL-R-71126(AR), 3.15.7 Targeting and Accuracy” (also from Wikipedia).

Could this help explain the 0.35 MOA test accuracy versus 1.0 MOA field accuracy?

 

[lockingblock]

I haven’t dug through the specs in a while, but I don’t think M118lr is even capable of that level of precision If they are measuring extreme spread. The original 7.62 was M852, if I recall correctly, and it was 1MOA on a very good day.

I would guess they are using some kind of alternative group measure like average mean radius or similar…rather than a 10 shot extreme spread.

The current precision load is MK 316, but it’s basically just federal gold medal cloned.

The M24 was not a great rifle. It was hastily assembled from off the shelf components of the era…and was never intended to be a long term program. It was a stop gap until a 300 win platform could go through full development. It’s why it was a long action.

The M2010 was what the M24 should have been and I think the 2010 is gone or going away as well.

DoD sniper systems, outside SOCOM, are historically way behind the technology curve.

 

[wvhunt]

Barrel life means different things to different people. While a 1/8" loss of accuracy at 100 yards would be shot out to a target shooter, the average hunter would probably never notice. So how many rounds to "shoot out a barrel" can vary depending upon who you're asking. I've had a couple varmint rifles start showing a slight loss in accuracy, so to me they were shot out.

I agree with the others about improper cleaning and how the guns are shot makes a huge difference. The late Warren Page said that barrels are actually burnt out, so letting them heat up makes a big difference in barrel life.