How many shots before cooling the barrel?

[Varminterror]

Thinking of barrel life and widely accepted notions - Equally, I have another itch I can’t scratch regarding barrel life:

It’s widely accepted that shooting a lower node/lower velocity/lower pressure/lower charge weight should improve barrel life. I had never experienced my own data in this stroke with a truly valid comparison until recently - in other words, as an example, I have shot out 22-250’s faster than 223rems, 7RM’s faster than 7-08’s, 300wm’s and WSM’s faster than 308’s, but obviously those comparisons are not just single variable experiments.

For that matter, I hadn’t considered this particular variable, but it’s also widely accepted a faster twist should burn out faster than a slower twist.

So my limited data from a relatively valid single variable change matrix:

I shot a low node charge in my 6 creed barrel last season, a grain and a half lighter charge, with 20thou longer seating depth (SAAMI chamber vs. custom throat for 105 Hybrids), and ~200fps slower than my load this season. My barrel last year lost 120fps by 500 rounds, was losing ~15fps per 100rnds by 1000, then would lose ~30-35fps per 100 rounds from 1,000 to 1471, when I pulled it off. I felt stuck with that barrel for half of the season last year, and I did a LOT of practice with other rifles trying to keep shots out of that barrel. I had expected far better life than that, based on my experience shooting 243’s and Dashers, and I REALLY thought I would improve my barrel life by shooting a relatively reduced load. That barrel was toast after 700, and hanging by a thread by the time I took it off.

This was a 1:8” twist barrel.

But...

This season, pushing harder, faster, and hotter as described above (and assuredly higher pressure, without poking too hard that particular bag of worms), my barrel lost 30fps after cleaning at ~1,000 rounds, and I’m going into State PRC finals next weekend with 1440 on the barrel, only slipping another ~10fps (which very well might just be the fact I have 2 more firings on the brass).

This is a 1:7.5” twist barrel.

By all common belief, the lifespans for these two barrels are backwards. The faster twist, higher pressure, heavier charge weight, higher velocity barrel has lasted a lot longer than the slower twist, slower velocity, lower pressure, lower charge weight barrel.

I can’t reconcile that comparison, and can’t reconcile the divergence with the widely accepted notion. Well, can’t reconcile it, other than to say sometimes we have to accept that barrel life is highly variable, a complex subject, and we can’t really define expectations with high precision. Being off by a few hundred rounds between identical barrels with identical loads would be very reasonable.

 

[Varminterror]

I won’t speak towards rapid fire burning out a barrel faster than slow fire, However I will say that I have noticed increased throat erosion seems to go hand and hand with increased powder charges.
No scientific test results you understand rather just an extra thousand every couple hundred rounds when checking CBTO type thing.
Does that count ??

We were posting at the same time, but my last message above taps this particular notion. I fully expect “higher charge weight = less barrel life,” but my last two 6 creed barrels were grossly opposed to that notion.

I expect it was anomalous, but that in itself illustrates the precision of barrel life expectations. A ballpark at best - and a big one at that.

 

[JFrank]

Did we just agree on something?

 

[cfullgraf]

Here is my experience and the barrel life info that may be dated.

I have a 204 Ruger AR-15 that the barrel is losing accuracy after 2000 rounds or so. The rifle has been one of my main prairie dog guns and at times I abuse the barrel with many shots in a short period of time. I do prefer to not let the barrel get too hot to touch but that is not always possible when the prairie dogs are plentiful. As been said, good AR-15 barrels are not too expensive and easy to change. I am getting ready to replace the barrel on this rifle, parts are on hand, I just need to schedule the work.

When I was shooting some Service Rifle competition around 2005, it seemed many competitors would experience degradation of accuracy at around 3000 rounds or so. The rapid fire stages in Service Rifle are 10 rounds in about one minute. Then the barrel can cool while setting up for the next rapid fire stage.

As several have said, a high round count of shooting in a short period of time will wear a barrel out faster than a slow rate of fire. I have a small battery power blower that can be inserted in the chamber and blow air down the barrel. It can help move air down the barrel to cool it faster than allowing ambient air cool the barrel.

So, I guess, shooting to make a barrel last just depends on your shooting frequency and loads.

 

[Demi-human]

...And personal accuracy or velocity requirements.


I would perhaps be happy with one of Varmint's barrels for some time after he is frustrated with it.

But I have no points at stake...

I will be in awe of the light recoil and still dramatic terminal effect. And still marvel at the best accuracy I've seen, since my targets are bigger. And furrier. And closer.
(I'm not very good.)

 

[whatnickname]

Stellite is a cobalt-chromium alloy. The US military has been using them in various machinegun barrels since just after WWII. The stellite is a liner made separate from the rest of the barrel and then usually cryogenically cooled and hydraulically pressed into the barrel. Some times another piece of steel is then put in behind the stellite where the chamber is then machined, sometime the chamber is machined into the stellite. The stellite liner typical goes about 15-20 calibers down the barrel from the chamber. Since the stellite liner has to have the riflings machine in before it's inserted into the steel barrel it takes specialized presses that can hydraulically insert the stellite liner and ensure the rifling in the liner lines up with those in the steel barrel.

Thank you for sharing that. Makes sense.

 

[taliv]

Thinking of barrel life and widely accepted notions - Equally, I have another itch I can’t scratch regarding barrel life:

It’s widely accepted that shooting a lower node/lower velocity/lower pressure/lower charge weight should improve barrel life. I had never experienced my own data in this stroke with a truly valid comparison until recently - in other words, as an example, I have shot out 22-250’s faster than 223rems, 7RM’s faster than 7-08’s, 300wm’s and WSM’s faster than 308’s, but obviously those comparisons are not just single variable experiments.

For that matter, I hadn’t considered this particular variable, but it’s also widely accepted a faster twist should burn out faster than a slower twist.

So my limited data from a relatively valid single variable change matrix:

I shot a low node charge in my 6 creed barrel last season, a grain and a half lighter charge, with 20thou longer seating depth (SAAMI chamber vs. custom throat for 105 Hybrids), and ~200fps slower than my load this season. My barrel last year lost 120fps by 500 rounds, was losing ~15fps per 100rnds by 1000, then would lose ~30-35fps per 100 rounds from 1,000 to 1471, when I pulled it off. I felt stuck with that barrel for half of the season last year, and I did a LOT of practice with other rifles trying to keep shots out of that barrel. I had expected far better life than that, based on my experience shooting 243’s and Dashers, and I REALLY thought I would improve my barrel life by shooting a relatively reduced load. That barrel was toast after 700, and hanging by a thread by the time I took it off.

This was a 1:8” twist barrel.

But...

This season, pushing harder, faster, and hotter as described above (and assuredly higher pressure, without poking too hard that particular bag of worms), my barrel lost 30fps after cleaning at ~1,000 rounds, and I’m going into State PRC finals next weekend with 1440 on the barrel, only slipping another ~10fps (which very well might just be the fact I have 2 more firings on the brass).

This is a 1:7.5” twist barrel.

By all common belief, the lifespans for these two barrels are backwards. The faster twist, higher pressure, heavier charge weight, higher velocity barrel has lasted a lot longer than the slower twist, slower velocity, lower pressure, lower charge weight barrel.

I can’t reconcile that comparison, and can’t reconcile the divergence with the widely accepted notion. Well, can’t reconcile it, other than to say sometimes we have to accept that barrel life is highly variable, a complex subject, and we can’t really define expectations with high precision. Being off by a few hundred rounds between identical barrels with identical loads would be very reasonable.

I shot out 11 barrels of 260ai. One broughton the rest bartlein. When I started and was pushing 140vld from 3020-3050 (yes very hot lol) I only got 1500-1600 rounds on barrels but when I backed it off to 2970-3000 I got 2000 rounds life

 

[Varminterror]

I shot out 11 barrels of 260ai. One broughton the rest bartlein. When I started and was pushing 140vld from 3020-3050 (yes very hot lol) I only got 1500-1600 rounds on barrels but when I backed it off to 2970-3000 I got 2000 rounds life

How many barrels at the slower speed vs. higher out of those 11?

This is exactly what I’d expect, as most of us would. I was VERY surprised at the abysmal life of my Rock Creek barrel last season. As I mentioned above, I think that one barrel was a fluke, an anomalous result, but it was the first time I had really committed to running lower charges. I often don’t run Max loads, but almost always run the high node in my rifles. I was expecting to improve a ~1,500 round expected life for 6 creed to something around 2,000 by running a grain and a half below max, but it certainly didn’t pan out for me - the damned thing burned out EARLY, not late. I can point to science which says barrels don’t care about how hot they get when fired, but I certainly can’t defend a lower node burning out faster than a higher node.

I’m surprised only cutting 100fps added that much barrel life for you - but alternatively, yes, 3050 with the 140’s is flat cooking (I expect 26”?), so it makes sense those tubes were smoked by 1600!

 

[taliv]

Lol my lapua brass was smoked too

I’d have to dig through old barrel books (I used to keep one book per barrel) to find out. I’m not at home now though.

I can’t explain your results. Are all your barrels rock creek? That might explain it.

 

[Varminterror]

No - that was the first, and last, Rock Creek barrel I will use. I spoke with their tech when it started going downhill, the guy told me he usually got 4000-5000 rounds on 6 creed barrels before he loses velocity, claiming H4350 and 105 Hybrids or 108 ELD’s the same as I was shooting.

But yes, I expect that is the only means of explaining that result: either it was one bad Rock Creek barrel, or theirs don’t last as long as Bartlein, Shilen, Krieger, or Lilja barrel. After the silliness talking to their tech, I washed my hands.

 

[taliv]

My last conversation with mike years ago was about him using tool steel in barrels to improve their life.