#30384
Sgt. Mike
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Ok even this was discussed as CA Dude and I went back and forth before I started this thread.
What is barrel life?

After two wall lockers being thrown across the room, six desk kicked over, terrorizing the building’s population to the degree that the Officer’s had to seek shelter from the fallout. This kinda happens when two opinionated Senior NCO civilly discuss matters they hold dear.
We both came to the conclusion that the lack of standards across population of shooters expectation / definition prohibit a accurate / accepted definition of barrel life.
Except for when the throat and bore are worn to the degree that the bullet goes sideways, or when expectations are not met.

This is why the Civilian sector does not do tests as everyone could and would challenges the results. Where as DoD has a listed MOA acceptance area and establishes standards they adhere to within the testing disagreements are not allowed the results are the results any mention of what if is considered outside the parameters and is not entertained nor allowed.
So however several shooters have attempted to do so over the years such as Mike Crawford in eastern NC he based his predictive spread sheet on Bart Bobbit and is continually refining based on input from a shooter base here is what Bart Bobbit said years ago:

From: Bart Bobbitt
Subject: Calculating Rifle Barrel Life

I finally completed my research on a way to calculate how many rounds
a rifle barrel can be expected to deliver its accuracy level. By that,
I mean the barrel can be expected to have an average group size for
so many rounds before that average group size starts to get larger.

First, the rule-of-thumb formula I derived will produce a barrel accuracy
life of about 3000 rounds.

Second, if a lot of rapid fire (one shot every 5 to 10 seconds) is done,
the accuracy life will be less.

Third, if full-auto or very fast fire (a few shots per second, or one shot
every second) is done, accuracy life will be much less.

Fourth, the accuracy levels are for ranges through 600 yards. Once the
barrel life calculated limit is reached, groups will probably start to
get bigger at the longer ranges before they are noticeably bigger at the
shorter ranges.

My formula, or rule-of-thumb process, is:

1. Calculate the bore area in square millimeters.

2. Use one grain of powder for each square millimeter. This is what
I call the reference, or base powder charge.

Example: .30 caliber bore = 45.6 square millimeters.
Base powder charge for .30 caliber is 45.6 grains.

A .30 cal. cartridge that burns 45.6 grains of powder should give a
barrel life of about 3000 rounds of good accuracy.

3. If a larger cartridge is used and it burns more powder, the
accuracy life in rounds for that bore size is reduced. The amount
of reduction is determined by

a. Divide the increased charge by the base charge, then square
the answer.

b. Divide that answer into 3000.

Example: .28 caliber bore has a base charge of 38.5 grains.
Cartridge burns 57.8 grains of powder.
(57.8/38.5) squared is 2.25.
3000 divided by 2.25 is 1,333 rounds.

If anyone can shoot a hole through this theory, I welcome that shot. This
is more or less an emperical process based on accurate barrel life in
several calibers as reported to me by lots of folks. All I did was study
the data and determine what math would give a best-fit formula.

And if someone has a better method, I’d like to know what it is. My
formulas may not be the best.

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