Question: Does shooting heavy bullets reduce barrel life?

[KevinThomas]

Necchi,

For what its worth, my predecessor at Sierra, Martin (Jim) Hull, used to use AP rounds for barrel break-n with his match rifles. Jim was a long time HP shooter of tremendous experience, a veritable fixture at Camp Perry for several decades. Still, at that time, THE Service Rifle was probably an M1, and might have been an M14 for a shooter on the military teams, and a Match Rifle was most certianly an M70 in 308. Might have been a few still clinging to the 30-06 as well, but it wasn't the diversity we see today. Old habits like this die hard in our community, especially in the absence of hard, scientific testing to verify or refute "common knowledge" passed down from shooter to shooter. I can't picture AP (or Tracer, for that matter) as being helpful to a barrel, but it clearly didn't do anything too terrible to them, either.

Kevin Thomas
Lapua USA

 

[KevinThomas]

George,

No offense taken at all, I assure you. My point was merely that things have changed over the years, and that some of the older studies (especially where the military is concerned), need to be looked at in light of todays conditions and developments. That, and the fact that we can only speak of barrel life if we also include the application; they ain't all the same! I mentioned the 3K figure for my 308 test barrels, which you seemed to concur with for XC and LR type shooting. I'm sitting here reading Tony Boyer's new book on rifle accuracy, a topic I'd have to say he knows a little about. Tony said flat out that he won't even attend a small local match with a barrel that has 700 rounds through it, and has seen some shot out at as little as 300 rounds. These are 6mm PPCs with light bullets, not some hotly loaded 6.5x284 with 139-142 grain bullets. It all comes down to a matter of what's required by the specific game we're playing, and they vary considerably.

Perhaps Tony summed it up best with one simple comment he made in the section on barrel life, "A simple truth; when you fire the first shot thru your barrel, that barrel is on its way dowwnhill." (emphasis in his original text) And that's perhaps the only truism that applies to all of us , regardless of our chosen discipline.

Kevin Thomas
Lapua USA

 

[shortgrass]

when you fire that first shot through your barrel, that barrel is on its' way down hill,,,,, I'll second that, for sure! As for setting back and re-chambering, experienced match shooters recognize and understand. The ones the average guy brings in are usually way too gone to be a viable candidate for this as erosion has worked its way foreward so far that a re-chambering won't get to good rifling.

 

[bigedp51]

Those that fail to learn from history are doomed to repeat it.....

Powder burn time and temperature have the greatest effects on barrel life.

Barrel wear and a steak have much in common.........
rare, medium, well done and charcoal, at 43,000 cup chamber pressure the peak flame temperature is approaching the melting point of modern barrel steel. A .222 Remington barrel will last longer than a .220 Swift. (time and temperature)

The British Enfield rifle shot ammunition loaded with Cordite a double base powder containing 23% nitroglycerin which burned at a higher temperature than a single base powder. British machine guns used on the ground or in the air were to use single base powder ammunition to extend barrel life and accuracy.

Armourer piercing ammunition has a steel core and the bullet does not upset to fill the bore diameter. High temperature gas leakage around the armourer piercing bullet causes erosion, the same can apply to boat tail bullets if they do not upset in the bore.

Below.
Mk.7 ammunition is cordite double base ammunition.
Mk.8z ammunition is single base ammunition with a deterrent coating on the powder.

Please read carefully below.

In conclusion as further evidence, the WWII Australian soldier below has fired an excessive amount of hot burning cordite powder ammunition. This in turn has caused all his hair to fall out and has given his skin a sickly near death like waxen pallor. :

 

[kombayotch]

It's the other way around...

All things being equal (same peak pressure, powder, primer, etc...), the lighter bullet load is burning more powder.
http://www.accurateshooter.com/technical-articles/excel-formula-predicts-useful-barrel-life/

 

[KevinThomas]

Bigedp51,

Throw another example of this into the mix here; when the Springfield '03 was first adopted (in its original guise, chambered for the .30-'03), the original load was a 220 or 230 grain RN-FMJ bullet. Inital tests gave an accuracy life of about 800 rounds. While this was with a heavy bullet, the real culprit there was the use of Hi-Vel #2, a double base powder with an extremely high NG content. The load was changed to another powder (have to dig up what that was) and the bore life issue was largely resolved. All became a moot point when we rechambeered these all to the new .30-'06 shortly thereafter.

I've mentioned before that it basically takes X pounds of powder to wash out a barrel. Whether that comes in many smaller doses, as in the 222 Rem, or fewer larger doses as in the 220 Swift, it's still X pounds of powder. The other factors are just related variables that go into the equation. The issue in question here was specific to the use of heavy bullets, but it's a complicated relationship, and a mistake focus on only one item with so many other variables in play.

Kevin Thomas
Lapua USA

 

[RonAKA]

I've mentioned before that it basically takes X pounds of powder to wash out a barrel. Whether that comes in many smaller doses, as in the 222 Rem, or fewer larger doses as in the 220 Swift, it's still X pounds of powder.

Kevin, I take it you are saying that it is X pounds of powder in the same caliber? What I am getting at is that I would expect you could fire one heck of a lot more powder out of a 30-06 than out of a .25-06. In the same caliber I do agree it is just the total heat you put down that small bore.

 

[KevinThomas]

Ron,

Exactly. As in, 308 vs a 300 RUM, that sort of thing. Same bullet weights, same pressure ranges, just a great deal more powder in one than the other. When we start throwing in different calibers (bore sizes) that skews the eqation and it becomes an unfair comparison. I wrote a piece some years back about this regarding two "identical" rifles of mine; same bore, same make barrel, same twist rate, etc.. The only difference was chambering. One was a 6x45mm (which I still have) and the other was a 240 Gibbs, that burned almost exactly twice as much powder. BIG difference in barrel life, and the Gibbs has long since been rebarreled.

Most of this comes from testing experience with things like the 6mmBR, which I used for both 70 grain bullets and for the 107s. The barrels used for the heavy bullets had probably one half to one third the barrel life as the ones used for the 70 grainers. Saw the same pattern over the course of dozens of barrels.

Kevin Thomas
Lapua USA

 

[fdshuster]

Exactly what I'm watching with a couple of my 6BR's. A 14 twist Shilen with a life of nothing but 68 gr. Bergers, vs a Hart 6BR 8 twist with all 95 & 107 gr. The total number of rounds fired in each is within 250, and the 8 twist is waiting to be replaced now. Meanwhile, the 14 twist shows no sign of any significant throat erosion.

 

[bozo699]

Frank,
Nice post, its hard to beat first hand experience. How many total rounds did you get out of the hart then?
Wayne.

 

[fdshuster]

Wayne: Forced to stop using the 8 twist at 1984 rds. Just too many uncalled flyers and copper fouling increased greatly. Rifle averaged 1 1/4" 5 shot groups at 300 yds. when new, 18 months ago, now barely holds m.o.a. Standard loads were 31 grs. of varget with the 95 gr. Sierra & Bergers then 30 grs. of Varget with the 107 gr. Sierra when throat depth became a problem for seating to touch with the 95's. Meanwhile, the 14 twist at 1725 rds. fired just keeps rolling along, doing its' thing, which is 5 shot groups at 300 yd. ( no wind) that average 3/4" to 1". Standard load has always been 30 grs. of N133 with the 68 Berger #24411 seated to touch. Barrel heat was always considered and kept it to a minimum with both. Would never try to claim this is what everyone can expect, just my experience with these 2 in particular.

 

[bozo699]

Frank,
Thanks, this gives me a idea of round count anyway. Mine won't be quite as high as I am going to blow out to 6brx 1:7.5 or 1:8 I want to shoot 105s 107s or 115s whatever the rifle says it likes. I want to take it to Montana and whip TheBlueEyedBear
with it Ha Ha
Wayne.

 

[RangerRob]

The flip side to this is that the heavier bullets offer better performance at distance, and hence are the logical choice for such applications. No such thing as a free lunch, and when you need the performance, you have to match the bullet/load to that application. Don't get attached to your barrel; they're strictly a replacement part, temporarily attached to your action. They're expendable, and the only way to not wear them out is to not use them.

Kevin Thomas
Lapua USA


;D Well said Kevin! ;D LMAO

 

[fdshuster]

"Ranger": 100% in agreement, and that's why I don't use bullets any heavier/longer than necessary to get the job done. 70 gr. and lighter are kept for 300 yd and less, and the heavier are not used unless distances are beyond 300 yds. Just my opinion, but I consider it a complete waste to use 107 gr. (as an example) at 1 and even 200 yds. And yes, barrels are expendable, no different than powder, primers, bullets and brass. I've been averaging 3 or 4 new barrels each year for the last 10 years, so am well aware of their limited life.

 

[tunacan]

How many people do you actually know that shoot a 45-70? How many people actually have shot their 45-70 enough to give an experienced opinion on barrel life?

 

[bozo699]

How many people do you actually know that shoot a 45-70? How many people actually have shot their 45-70 enough to give an experienced opinion on barrel life?

I don't know, I shot my 45/70 about 30 times today, I don't think I hurt the barrel life any but I can't say the same for my shoulder LOL
Wayne.

 

[gerard1977]

I'm bringing this post back to life to answer some of the questions here for people like myself that stumble across it while searching google. There is an observation made here and in other forums that heavier bullets erode the throat quicker than lighter bullets. Without knowing the types of powder, quantities, and bullet weights used its hard to have a formal hypothesis. However, we can use the example of the 30 grains of n133 with a 68 grain berger vs. the 30 grains of varget with the 107 grain sierra mentioned earlier in this thread. The noticed behavior was that the 107 grains wore out the throat quicker than the 68 grains. One explanation is this. The n133 has a powder heat potential of 3650 kJ/kg while the varget has a powder heat potential of 4050 kJ/kg. Usually when loading heavier bullets the powder charge is reduced however, that isn't the case here. Pressures for the n133 with the 68 grain bullets should have been somewhere around 55k. Pressures for the varget with the 107 grain bullets should have been around 59k. Both guesses from quickload. The heavier bullet is using powder with a much higher heat potential and firing at much higher pressures and the exact same number of grains of powder is being used. The barrel life excel spreadsheet at http://www.leroyrifleandpistolclub.org/powder-heat-potential.html accurately predicts that the heavier weight bullet in this specific example would have roughly half the barrel life of the n133 barrel. The heavier weight bullet in this particular example didn't have near as much effect as the type and quantity of the very hot burning varget powder. I am very sure that the light load mentioned in this example wasn't fired at near the distances the heavier load was and this is why the heavier bullet required a much hotter powder charge. So perhaps it isn't the heavier bullets that wear the barrels, but instead the functional use of the heavier bullets and the desire to have them achieve greater accurate distance than lighter bullets.

 

[ireload2]

Check item 18 on this list.
It is about testing to a barrel life of about 30,000 rounds.

http://www.frfrogspad.com/bal1indx.htm

 

[mic2377]

I think this is a complicated question, because there is not only the variable of bullet weight but also powder type and weight.

My experience is primarily with 223 and 308. It is fairly well documented that use of high energy powders like Varget and heavy bullets cause accelerated gas port erosion, in addition to shortening barrel life. My guess is that a combination of increased barrel time, longer bearing surface, and high heat of combustion from a high energy single base powder like Varget is responsible for this.

In comparison a 223 shooting 50-55 gr bullets with a ball powder like Win 748 seems to last just about forever, even with relatively high rates of fire...

 

[AckleymanII]

I can tell you for a fact that in custom 223's and AI's with 50g-55g bullets, that N133 and N135 are barrel eating son of guns!