Twist rate and barrel life.

Lavan · November 20, 2019, 10:07 AM

Is there any appreciable difference in barrel life attributable to twist rate?

Just curious as it SEEMS that pushing something really fast against a tighter twist would get everything hotter.

Jim Watson · November 20, 2019, 10:43 AM

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.

pblanc · November 20, 2019, 01:36 PM

Yes, everything else equal (which is never the case) the faster the barrel twist creates more total friction and slightly accelerates wear on the lands.

T. O'Heir · November 20, 2019, 02:08 PM

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.

Lavan · November 20, 2019, 02:11 PM

Tungsten carbide bullets could speed the test a whole bunch, I bet.

Jim Watson · November 20, 2019, 02:55 PM

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.

Lavan · November 20, 2019, 03:18 PM

SEE???

Even the ARMY was worried.

HiBC · November 20, 2019, 04:18 PM

There are a number of variables at work.How often is twist the only variable?
Generally tighter twist means heavier bullets,slower powder.and lower velocity

Bart B. · November 20, 2019, 04:40 PM

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.

Ben Dover · November 20, 2019, 06:00 PM

If you can afford the ammunition needed to burn out a barrel, the cost of replacing that barrel would be of little or no concern!

bamaranger · November 21, 2019, 01:22 AM

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.

Bart B. · November 21, 2019, 01:57 PM

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.

SIGSHR · November 22, 2019, 03:05 PM

IMHO barrel steel is more important. Also powders used. IIRC the .220 Swift is hard on barrels, the powders used for the M1895 Lee Navy contributed to fast barrel wear.

Bart B. · November 22, 2019, 04:08 PM

Quote:

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.

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.

bamaranger · November 22, 2019, 08:53 PM

Bart B.

Pretty interesting, I'd not heard of that, Sierra is the company, thanks for the tip.

November 20, 2019, 10:07 AM	#1
Lavan Senior Member Join Date: December 10, 1999 Location: California Posts: 2,716	Twist rate and barrel life. Is there any appreciable difference in barrel life attributable to twist rate? Just curious as it SEEMS that pushing something really fast against a tighter twist would get everything hotter.

November 20, 2019, 02:08 PM	#4
T. O'Heir Senior Member Join Date: February 13, 2002 Location: Canada Posts: 12,453	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. __________________ Spelling and grammar count!

November 20, 2019, 04:40 PM	#9
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	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. Last edited by Bart B.; November 20, 2019 at 05:04 PM.

November 20, 2019, 06:00 PM	#10
Ben Dover Senior Member Join Date: April 11, 2013 Location: High up in the Rocky Moun Posts: 665	If you can afford the ammunition needed to burn out a barrel, the cost of replacing that barrel would be of little or no concern! __________________ The soldier's pack is not so heavy a burden as the prisoner's chains. Dwight Eisenhower It is very important what a man stands for. But it is far more important what a man refuses to stand for.

November 21, 2019, 01:22 AM	#11
bamaranger Senior Member Join Date: October 9, 2009 Location: North Alabama Posts: 8,308	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.

November 20, 2019, 10:43 AM	#2
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,541	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.

November 20, 2019, 01:36 PM	#3
pblanc Senior Member Join Date: March 23, 2008 Location: Indiana Posts: 697	Yes, everything else equal (which is never the case) the faster the barrel twist creates more total friction and slightly accelerates wear on the lands.

November 20, 2019, 02:11 PM	#5
Lavan Senior Member Join Date: December 10, 1999 Location: California Posts: 2,716	Tungsten carbide bullets could speed the test a whole bunch, I bet.

November 20, 2019, 02:55 PM	#6
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,541	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.

November 20, 2019, 03:18 PM	#7
Lavan Senior Member Join Date: December 10, 1999 Location: California Posts: 2,716	SEE??? Even the ARMY was worried.

November 20, 2019, 04:18 PM	#8
HiBC Senior Member Join Date: November 13, 2006 Posts: 8,286	There are a number of variables at work.How often is twist the only variable? Generally tighter twist means heavier bullets,slower powder.and lower velocity

November 21, 2019, 01:57 PM	#12
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	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. Last edited by Bart B.; November 21, 2019 at 02:04 PM.

November 22, 2019, 03:05 PM	#13
SIGSHR Senior Member Join Date: September 13, 2005 Posts: 4,700	IMHO barrel steel is more important. Also powders used. IIRC the .220 Swift is hard on barrels, the powders used for the M1895 Lee Navy contributed to fast barrel wear.

November 22, 2019, 08:53 PM	#15
bamaranger Senior Member Join Date: October 9, 2009 Location: North Alabama Posts: 8,308	rounds per minute Bart B. Pretty interesting, I'd not heard of that, Sierra is the company, thanks for the tip.