Twist rate and barrel life.
- Thread starter Lavan
- Start date
Jim Watson
New member
As the one gunzine writer said, you would have to systematically wear out several barrels to find a difference, if any. Got lots of time, barrels and ammo? I don't.
No.
"...faster the barrel twist creates more total friction..." That is not, in any way, true. The twist is about stabilizing the bullet according to its weight and nothing else.
Barrel life means different things to different shooters too. The Bench Rest guys(to whom we all owe a great deal) will tell you a barrel is worn out if it won't give under 1/10" or less groups at 100 yards or more. A deer hunter will say more than 3" consistently.
"...faster the barrel twist creates more total friction..." That is not, in any way, true. The twist is about stabilizing the bullet according to its weight and nothing else.
Barrel life means different things to different shooters too. The Bench Rest guys(to whom we all owe a great deal) will tell you a barrel is worn out if it won't give under 1/10" or less groups at 100 yards or more. A deer hunter will say more than 3" consistently.
Jim Watson
New member
There was considerable concern over the chance that the M16A2 barrel with 7 twist would not last as long as the previous 12 twist. I haven't heard anything about it since it became so common.
Use an on-line right angle calculator to compute the rifling angle presented to the bullet. Bore circumference is one entry, twist length is the other.
A 1:8" twist in 22 caliber barrels has the same ~5 degree rifling angle to the bullet as a 1:11" twist in a 30 caliber barrel. 22 caliber barrels with a 1:7" twist has the same angle of rifling as a 30 caliber one with a 1:9.6" twist.
A 1:8" twist in 22 caliber barrels has the same ~5 degree rifling angle to the bullet as a 1:11" twist in a 30 caliber barrel. 22 caliber barrels with a 1:7" twist has the same angle of rifling as a 30 caliber one with a 1:9.6" twist.
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bamaranger
New member
rate of fire
I think that rate of fire and velocity are two big factors on barrel life, as they contribute directly to barrel temps, higher temps break down steel. Velocity is often achieved with an overbore condition, large charges of powder down small caliber tubes, one example being the old .220 Swift and another the .264 Mag. I have never read or heard of twist rate having a bearing on barrel life, but I certainly could be wrong.
I think that rate of fire and velocity are two big factors on barrel life, as they contribute directly to barrel temps, higher temps break down steel. Velocity is often achieved with an overbore condition, large charges of powder down small caliber tubes, one example being the old .220 Swift and another the .264 Mag. I have never read or heard of twist rate having a bearing on barrel life, but I certainly could be wrong.
I don't think any rate of fire up to 10 shots per minute shortens barrel life. That's what Sierra testing bullets for quality does, one group every 10 minutes during a production run. They get the same barrel life as a match rifle does shooting one shot per minute. About 3000 rounds or a little more with a 308 Win barrel.
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Reality is, they rebarrel when the largest test groups go over around 1/4th". When all the variables cancel each other out at that time of the barrel's life, a sub 1/10ths" group will occasionally happen.
Look up some benchrest 100 yard aggreate records for several 10-shot groups then note the size of the average. Biggest group is 20 to 30 percent larger. None of those agg's is under one tenth inch.
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bamaranger
New member
rounds per minute
Bart B.
Pretty interesting, I'd not heard of that, Sierra is the company, thanks for the tip.
Bart B.
Pretty interesting, I'd not heard of that, Sierra is the company, thanks for the tip.