This is a great short story on barrel life

[Trapper]

Borrowed from Accurateshooter.com

Gone in Six Seconds — The Shocking Truth of Barrel Life
Here’s a little known fact that may startle most readers, even experienced gunsmiths: your barrel wears out in a matter of seconds. The useful life of a typical match barrel, in terms of actual bullet-in-barrel time, is only a few seconds. How can that be, you ask? Well you need to look at the actual time that bullets spend traveling through the bore during the barrel’s useful life. (Hint: it’s not very long).

Bullet-Time-in-Barrel Calculations
If a bullet flies at 3000 fps, it will pass through a 24″ (two-foot) barrel in 1/1500th of a second. If you have a useful barrel life of 3000 rounds, that would translate to just two seconds of actual bullet-in-barrel operating time.

Ah, but it’s not that simple. Your bullet starts at zero velocity and then accelerates as it passes through the bore, so the projectile’s average velocity is not the same as the 3000 fps muzzle velocity. So how long does a centerfire bullet (with 3000 fps MV) typically stay in the bore? The answer is about .002 seconds. This number was calculated by Varmint Al, who is a really smart engineer dude who worked at the Lawrence Livermore Laboratory, a government think tank that develops neutron bombs, fusion reactors and other simple stuff.

Stopwatch barrel life

On his Barrel Tuner page, Varmint Al figured out that the amount of time a bullet spends in a barrel during firing is under .002 seconds. Al writes: “The approximate time that it takes a 3300 fps muzzle velocity bullet to exit the barrel, assuming a constant acceleration, is 0.0011 seconds. Actual exit times would be longer since the bullet is not under constant acceleration.”

We’ll use the .002 number for our calculations here, knowing that the exact number depends on barrel length and muzzle velocity. But .002 is a good average that errs, if anything, on the side of more barrel operating life rather than less.

So, if a bullet spends .002 seconds in the barrel during each shot, and you get 3000 rounds of accurate barrel life, how much actual firing time does the barrel deliver before it loses accuracy? That’s simple math: 3000 x .002 seconds = 6 seconds.
Stopwatch barrel lifeGone in Six Seconds. Want to Cry Now?
Six seconds. That’s how long your barrel actually functions (in terms of bullet-in-barrel shot time) before it “goes south.” Yes, we know some barrels last longer than 3000 rounds. On the other hand, plenty of .243 Win and 6.5-284 barrels lose accuracy in 1500 rounds or less. If your barrel loses accuracy at the 1500-round mark, then it only worked for three seconds! Of course, if you are shooting a “long-lived” .308 Win that goes 5000 rounds before losing accuracy, then you get a whopping TEN seconds of barrel life. Anyway you look at it, a rifle barrel has very little longevity, when you consider actual firing time.

People already lament the high cost of replacing barrels. Now that you know how short-lived barrels really are, you can complain even louder. Of course our analysis does give you even more of an excuse to buy a nice new Bartlein, Krieger, Shilen etc. barrel for that fine rifle of yours.

[wbm]

Cool. Very interesting data!

[Oscarflytyer]

That is very sobering! And hilarious! I love nerdville shooting and ballistics stuff!

[COplains]

So that would mean that a 22-250 with hot loads would last about 300 milli seconds! That PD just got way more expensive!

[Oscarflytyer]

Shared the metrics with my son. His eyebrows wen WAY up! Made him appreciate ballistics and shooting a lot more! Always a good thing!

[LoneWolf]

Blew my buddy away thinking about all the rounds he puts through his AR on a regular basis.

[tufrthnails]

Blew my buddy away thinking about all the rounds he puts through his AR on a regular basis.

I was thinking the same thing about my M4 while on that last deployment.

[chukarmandoo]

And thats why I hate shooting at 100 yds. In my mind's eye if it takes 1.5 to 2 seconds for the bullet to reach the target and I get 3000 rounds down the tube, then I feel I've extended the barrel life by quite a bit. Just sayin.

[DanSavage]

So the shorter the barrel, the less time the bullet will be in there. So shorter barrel = more barrel life?

[sharpshooter]

Barrel life can be more accurately measured by how much powder is consumed. The number of bullets going down the bore is inconcesquential, what degrades barrels is heat. It takes X amount of BTU's to destroy the guilt edge of accuracy, whether its spread over time or all at once. For most of the popular calibers, it takes about 13 lbs. of powder to render a good barrel to the class of being non-competitive. Of course, there are exceptions to the rule.

[Salvo]

Note that an already warm (or hot) barrel will get much hotter than usual if another round is immediately firedthrough it. - Thus reducing your few seconds of barrel life dramatically. With each rapid-fire round, the internal temperature (and the damage that follows) climbs to new levels.

With magnum or overbore cartridges like the .243 Winchester this effect is magnified.

If you let it cool off in-between shots, you are doing yourself a big favor as far as barrel life and accuracy is concerned.

Here is the throat, rifling lead area of a 7mm Remington magnum that looked new and unfired on the outside... Somebody thought it would be a good idea to rapidly fire a number of rounds through it. This barrel didn't even get one-half second of use before it was fried, no longer capable of useful accuracy.


Click image to see it larger.