Barrel life question
- Thread starter damullet
- Start date
OP - amidst the usual mix of bad information and posturing that goes along with any internet discussion you already have your answer:
Overbore cartridges generally have a shorter life span;
Running hot loads will increase the rate of wear;
A .308 is generally thought to have the longest useful life span and
Even when a barrel is past its' prime it can still be sufficiently accurate for hunting or casual shooting.
Overbore cartridges generally have a shorter life span;
Running hot loads will increase the rate of wear;
A .308 is generally thought to have the longest useful life span and
Even when a barrel is past its' prime it can still be sufficiently accurate for hunting or casual shooting.
Actually, Suputin is right.
Powder does not turn to hot gas in an instant but rather the kernels burn progressively from the surface inwards. The slower the powder the slower the kernels burn.
It comes to reason then, that at some point in time, there's going to be sand-like particles traveling at high speed in a very hot gas envelope.
This is what "sands" the throat smooth. Of course, the jacket material contributes to the abrasion.
The compressed air by comparison does not exhibit the sanding effect.
For a given cartridge and barrel length, higher velocity generally mean:
1) a lighter bullet
2) faster burning powder
3) a larger powder charge
4) higher velocities
My 6mm Crusader (basically a 6mm Rem AI) takes over 60 gr. of H4350 to reach maximum pressure with a 60 gr. bullet while it only takes ~53 gr. of Retumbo with a 115 gr. bullet to reach the same pressure. Velocities are around 3900 fps and 3100 fps., respectively. How do I know they are at the same pressure? Because I have equipment that measures it. Looking at the pressure curves, the ones with the light bullet peaks much faster and the curve is much narrower. This means that a larger quantity of powder is getting burned up over a shorter length of barrel. The barrel runs noticeably cooler with the 115gr. Retumbo load.
Varmint hunters shooting the 60 gr. H4350 load get around 1000 rounds before their barrel is toast. I get over 2000 rounds shooting the 115 with a smaller charge of slower burning Retumbo. Same cartridge running at the same peak pressure, but very different barrel life numbers.
You can't specify barrel life numbers for a given cartridge without specifying the load being shot in it the majority of the time. Especially, when there is a larger range of bullet weights for the caliber. It's like specifying the velocity of a cartridge without mentioning the weight of the bullet being fired. It's meaningless...
1) a lighter bullet
2) faster burning powder
3) a larger powder charge
4) higher velocities
My 6mm Crusader (basically a 6mm Rem AI) takes over 60 gr. of H4350 to reach maximum pressure with a 60 gr. bullet while it only takes ~53 gr. of Retumbo with a 115 gr. bullet to reach the same pressure. Velocities are around 3900 fps and 3100 fps., respectively. How do I know they are at the same pressure? Because I have equipment that measures it. Looking at the pressure curves, the ones with the light bullet peaks much faster and the curve is much narrower. This means that a larger quantity of powder is getting burned up over a shorter length of barrel. The barrel runs noticeably cooler with the 115gr. Retumbo load.
Varmint hunters shooting the 60 gr. H4350 load get around 1000 rounds before their barrel is toast. I get over 2000 rounds shooting the 115 with a smaller charge of slower burning Retumbo. Same cartridge running at the same peak pressure, but very different barrel life numbers.
You can't specify barrel life numbers for a given cartridge without specifying the load being shot in it the majority of the time. Especially, when there is a larger range of bullet weights for the caliber. It's like specifying the velocity of a cartridge without mentioning the weight of the bullet being fired. It's meaningless...
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1. Normal wear and tear from shooting.
2. Poor cleaning technique; for most rifles, this is probably the biggest wear factor.
3. Rapid fire and getting the barrel hot (like, really hot)
4. Double base powders are harder on the bore than single base
5. The longer the bearing surface of the bullet, the more bore wear.
6. The higher the velocity, the faster the bore will wear.
A combination of those factors is what uses up barrels. Only normal wear and tear is beyond your control, the shooter can control, to some degree, all the other factors.
Barrel life is probably drastically over thought however. It's really a minor expense in the overall scheme of things. If you're shooting out barrels, regardless if it's with a .416 Barret or a .223, re barreling is nowhere near the biggest expense involved. At $.50 a round, it's going to cost $2500 in ammo to shoot out a $300 .308 barrel. If it's a concern, set aside $10 a month in a piggy bank; $30 if you shoot competitively.
calvados.boulard
CGN frequent flyer
- Location
- Victoria BC
Could someone please provide an explanation of the overbore chart and graph shown in the first few posts that would be suitable for a numbskull like me to understand?
Thanks,
Cal.
Thanks,
Cal.
calvados.boulard
CGN frequent flyer
- Location
- Victoria BC
Also, when speaking of longer strings of fire, how many is too many? Is the rule of thumb something along the lines of "too hot to touch = too many"?
Thanks,
Cal.
Thanks,
Cal.
The more powder in relation to bore cross sectional area = shorter expected barrel life.
Take the .308 family of cartridges; they illustrate this perfectly. The .358 Win would have the longest expected barrel life, going down through the .308, 7-08, .260 finally to the .243 with the shortest expected.
Bigfoot 870
CGN frequent flyer
- Location
- Nova Scotia
He hauled his horns in.........see post #4.
I look forward to seeing you flame one of the crusty old veterans on here. Be prepared, when you do
You vying to be the next Sunray?
Where does a barrel wear the most? Where is the highest velocity and thus the most friction and its related heat?
The answers to these questions are that the barrel wears the most at the throat, where the velocities are the lowest. Thus if your theory was correct, the throat would experience the least wear while the area nearest the crown would experience the most due to being exposed to the highest velocities.
However the throat is exposed to the most burning plasma and thus wears the most while the crown is exposed to the least burning plasma and thus wears the least. Therefore outright velocity is not the issue. It is the amount of powder being forced down the bore that causes the wear.
See, no reason to be pisssy ...... especially when you are wrong.
calvados.boulard
CGN frequent flyer
- Location
- Victoria BC
Dumb question #49493 How does bullet weight play into barrel life? Is there any correlation between the two?
Thanks,
Cal.
Thanks,
Cal.
A look at any reloading manual will tell you exactly the opposite. For the same peak pressure, you need to use a lighter powder charge with a heavier bullet.
You will generally use a larger powder charge with a lighter bullet, and it will often be with a faster burning powder. This will torch the throat faster.
Yes... I didn't mean bullet weights within the same cartridge. What I was getting at is that there's considerably more powder driving a 200 gr .308 out of a .300 WM than a 150 gr .308 out of a .308 Win, and considerably more again than for a 75 gr .223, although of course charge weight alone is not a determinant of life.
Bigfoot 870
CGN frequent flyer
- Location
- Nova Scotia
You vying to be the next Sunray?
Where does a barrel wear the most? Where is the highest velocity and thus the most friction and its related heat?
The answers to these questions are that the barrel wears the most at the throat, where the velocities are the lowest. Thus if your theory was correct, the throat would experience the least wear while the area nearest the crown would experience the most due to being exposed to the highest velocities.
However the throat is exposed to the most burning plasma and thus wears the most while the crown is exposed to the least burning plasma and thus wears the least. Therefore outright velocity is not the issue. It is the amount of powder being forced down the bore that causes the wear.
See, no reason to be pisssy ...... especially when you are wrong.
Chinbullco
Regular
- Location
- NW Alberta
Maybe the time to reply to questions is when you know the answers. But thanks for trying to help.
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Gunnerlove
CGN Ultra frequent flyer
- Location
- Vancouver Island
I remember reading that Gerald Bull considered the burning granular powder to be physically abrasive. The lack of abrasive solids increasing barrel life was going to be one of the advantages of the liquid propellant Crusader SPH (actually working and not poisoning crews was the stumbling point).
RIP Gerald Bull
