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Ahhnother8
10-06-2009, 3:52 PM
Measured in hours, minutes, and seconds, what is the total amount of time that bullets are actually going down (in contact with) the bore, and the barrel will still shoot decent groups? Granted, it will depend upon the caliber, barrel, bullet, powder, velocity, and ones definition of 'decent'. So, what is the actual life expectancy of these 24" barrels? What is a rough time estimate, not round count, for:

.22 LR
.223
.220 Swift
6-.284
6.5-.284
.284
.308
.300 Wby.

Lane

technique
10-06-2009, 3:59 PM
It has to do with heat. No one can answer that for you. Heat kills barrels. Not time, not round count...

reidnez
10-06-2009, 4:02 PM
It would also depend to a great degree on the manufacturer's specs, the quality of steel they're using, how it's forged/machined, whether the barrel is chrome-lined, and the type of ammunition being used. Far too many variables here.

technique
10-06-2009, 4:04 PM
Here:

If I fired 365rnds rapidly right now it would do more damage than if I fired 1rnd every day for the next 365 days.

another:

My .243 barrel will wear more than my .308 barrel even if I fire them equally.

Ahhnother8
10-06-2009, 5:42 PM
My .243 barrel will wear more than my .308 barrel even if I fire them equally.

My point exactly!! But how many hours, minutes, and seconds will a bullet actually be in the bore? It's not a trick question. Do the math for each, and be astounded!!

gun toting monkeyboy
10-06-2009, 5:52 PM
None of us feel like doing that sort of mental heavy lifting at the moment. If you have the answer. please feel free to post it.

B Strong
10-06-2009, 5:59 PM
My point exactly!! But how many hours, minutes, and seconds will a bullet actually be in the bore? It's not a trick question. Do the math for each, and be astounded!!


I'll stick to round count and heat cycles, thank you.

Greg-Dawg
10-06-2009, 6:02 PM
Depends on the barrel...

Chrome moly.
Chrome lining.
Stainless?

CHS
10-06-2009, 6:21 PM
My point exactly!! But how many hours, minutes, and seconds will a bullet actually be in the bore? It's not a trick question. Do the math for each, and be astounded!!

It's a 100% useless statistic that I just don't give a damn about.

Round-count and duty cycle is all that really matters.

CSACANNONEER
10-06-2009, 6:24 PM
It's a 100% useless statistic that I just don't give a damn about.

Round-count and duty cycle is all that really matters.

Rond count doesn't mean as much as many people here think it does. I'd rather have an AR with 10K fired slowly through it than an AR with 1000 rounds fired at full auto speed without allowing the barrel to cool.

CHS
10-06-2009, 6:27 PM
Rond count doesn't mean as much as many people here think it does. I'd rather have an AR with 10K fired slowly through it than an AR with 1000 rounds fired at full auto speed without allowing the barrel to cool.

Hence, round count and duty cycle :)

Pthfndr
10-06-2009, 6:43 PM
My point exactly!! But how many hours, minutes, and seconds will a bullet actually be in the bore? It's not a trick question. Do the math for each, and be astounded!!

6.5x284? About 7.5 seconds?

Jpach
10-06-2009, 6:53 PM
6.5x284? About 7.5 seconds?

+1 ^^^^. OP, If a 6.5x284 has a barrel life of 1200rds (or whatever), I dont think the projectile-in-barrel time even amounts to more than several seconds, if that. I havent done the math but I used more of just common sense. Who knows though, I could be waaaaaay off.

Ahhnother8
10-06-2009, 6:58 PM
6.5x284? About 7.5 seconds?

You wish!!

Jpach has the right idea. The 6.5-.284 has an expected barrel life of approximately 1 to 1 1/2 SECONDS. The 6 -.284's life is about 3/4 of ONE SECOND.

Lane

Phil3
10-06-2009, 7:00 PM
Barrel life is dependent on many factors, but actual total time all bullets spend in the barrel being pushed out under pressure is very low.

Consider a 223 Remington at 3000 feet per second. It starts at 0 fps and gets to 3000 very quickly. I do not know the actual acceleration curve, but assume that the average velocity in the barrel is an average of 0 and 3000, or 1500 fps. In a 24" barrel, (two feet), it will take 2/1500 of a second for the bullet to exit, or .001333 second. If the average barrel life is 3000 rounds, then total time that bullets are firing down the barrel is 4 seconds (3000 x .001333). Since the bullet is up to speed early in the barrel, the average velocity down the length of the barrel is almost certainly higher, meaning the total time is even less than the 4 seconds stated.

- Phil

Phil3
10-06-2009, 7:16 PM
Equally amazing, consider the same 223 I mentioned above with a 1:9" twist barrel. At 3000 feet per second, the bullet is being spun 1.333 revolutions for every foot it travels forward. Since it is traveling at 3000 feet per second, that means the bullet is spun up to 240,000 rpm at that velocity. This is not unusual and bullets may be spun up to near to 300,000 rpm without flying apart. 1:7" at 2750 fps is 283,000 rpm.

If the bullet, .224" in diameter, now spinning at 240,000 rpm, was laid on the ground and rolled along on its side at this rpm, it would be traveling sideways (like a mini wheel), at 2,814 feet per second. That is 1,191 mph. Imagine a .224" diameter wheel traveling down the road at 1,919 mph and this is how fast that bullet is spinning when it leaves the barrel.

Getting to 240,000 rpm in .001 seconds also explains the torque reaction some rifles have as the bullet spins up in the barrel.

What I would like to know is how much the bullet slows down in spin on the way to the target. Spin may decrease in direct correlation with the decrease in velocity or more likely it is changing at some other rate.

- Phil

phish
10-06-2009, 8:29 PM
.223 is roughly 3 seconds, read it somewhere...

Pthfndr
10-06-2009, 8:32 PM
You wish!!

Jpach has the right idea. The 6.5-.284 has an expected barrel life of approximately 1 to 1 1/2 SECONDS. The 6 -.284's life is about 3/4 of ONE SECOND.

Lane

My standard of a worn out barrel is much lower than yours. You need to be able to shoot Xs, I just need to keep it on the paper somewhere :)

phish
10-06-2009, 8:38 PM
^ mine is when the shank of an 80 can't even fit in the neck anymore :eek:

22popnsplat
10-06-2009, 8:45 PM
you forgot about the squib that sat stuck in the barrel for years .

mocos
10-06-2009, 8:48 PM
Measured in hours, minutes, and seconds, what is the total amount of time that bullets are actually going down (in contact with) the bore, and the barrel will still shoot decent groups? Granted, it will depend upon the caliber, barrel, bullet, powder, velocity, and ones definition of 'decent'. So, what is the actual life expectancy of these 24" barrels? What is a rough time estimate, not round count, for:

.22 LR
.223
.220 Swift
6-.284
6.5-.284
.284
.308
.300 Wby.

Lane

well.... if you started with the .22 rimfire and started calculating in all the variables that could possibly affect the life expectancy of that particular barrel...you would probably still be calculating......when hell freezes over..and even then if you came up with a number/time....you would have to do it again to prove it's validity......get a life....

Ahhnother8
10-07-2009, 11:48 AM
Barrel life is dependent on many factors, but actual total time all bullets spend in the barrel being pushed out under pressure is very low.

Consider a 223 Remington at 3000 feet per second. It starts at 0 fps and gets to 3000 very quickly. I do not know the actual acceleration curve, but assume that the average velocity in the barrel is an average of 0 and 3000, or 1500 fps. In a 24" barrel, (two feet), it will take 2/1500 of a second for the bullet to exit, or .001333 second. If the average barrel life is 3000 rounds, then total time that bullets are firing down the barrel is 4 seconds (3000 x .001333). Since the bullet is up to speed early in the barrel, the average velocity down the length of the barrel is almost certainly higher, meaning the total time is even less than the 4 seconds stated.

- Phil

And there you have it. Thank you for taking the time to explain it to the noobs. It's pretty amazing that the useful life of most barrels is measured in seconds.

Are you still planning on coming to Sac on Sunday for the 600 yard match? If so, and you are interested, I will offer for you to shoot:

A) AR spacegun with a 26" Pac-Nor shooting 80 grain Berger VLD's at 2900 fps.

B) Swing Palma rifle with a 30" Krieger shooting 155 grain Carteruccio's or 155 grain SMK's at 3000 fps.

Not sure which one yet, will be testing ammo in Lincoln on Thursday. They have each won a LOT of matches, and are quite accurate. I will be shooting the AR on Saturday in the XTC match. Both have iron sights, but I could add a scope, if absolutely necessary. Also have front and rear rests, if F-class is your preference. If you are interested, let me know...

Lane

Lancear15
10-07-2009, 1:53 PM
deleted

rksimple
10-07-2009, 2:21 PM
What I would like to know is how much the bullet slows down in spin on the way to the target. Spin may decrease in direct correlation with the decrease in velocity or more likely it is changing at some other rate.

- Phil

Rotational velocity doesn't bleed off at even a fraction of MV. Something about vectors working independently of one another. Been a while since I've read up on it.

What say you Lane?

nrakid88
10-07-2009, 2:35 PM
I have no idea... but I do know that a 55 grain 5.56x45mm round coming out of a 20 inch upper with a 1 in 7 twist is spinning at about 350,000 rpm

Ahhnother8
10-07-2009, 2:36 PM
Rotational velocity doesn't bleed off at even a fraction of MV. Something about vectors working independently of one another. Been a while since I've read up on it.

What say you Lane?

I have no idea. External ballistics are fascinating though. As Phil pointed out, the RPM's are just insane. I know that the f-classers were vaporizing (shedding the jackets off) a lot of bullets, up until a couple of years ago. They were mostly shooting the 6.5-.284 with 140-142 grain bullets at 3000+ fps out of 1:7 or 1:7.5 twist barrels. Eric Stecker at Berger Bullets did a lot of research on the topic and they recently introduced the thick jacketed line of bullets for competition. The combination of velocity, RPM's, and barrel fouling all contributed to the problem. The new bullets stay together now, but they are expensive.

Phil3
10-10-2009, 5:31 PM
Are you still planning on coming to Sac on Sunday for the 600 yard match? If so, and you are interested, I will offer for you to shoot:

A) AR spacegun with a 26" Pac-Nor shooting 80 grain Berger VLD's at 2900 fps.

B) Swing Palma rifle with a 30" Krieger shooting 155 grain Carteruccio's or 155 grain SMK's at 3000 fps.

Not sure which one yet, will be testing ammo in Lincoln on Thursday. They have each won a LOT of matches, and are quite accurate. I will be shooting the AR on Saturday in the XTC match. Both have iron sights, but I could add a scope, if absolutely necessary. Also have front and rear rests, if F-class is your preference. If you are interested, let me know...

Lane

Lane, please see PM. - Phil