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mblat
02-09-2006, 8:23 PM
What would be the difference of life expectancy for barrel between 1x7 twist and 1x9 twist?
Anybody can point to any studies? I've read that 1x7 would wear of faster, but what does "faster" mean in bullet count?

Also if I shoot heavier bullets would that decrease life of the barrel compare wo lighter onces?

akjunkie
02-09-2006, 9:22 PM
everything u need to know......

http://www.ammo-oracle.com

mblat
02-09-2006, 9:39 PM
everything u need to know......

http://www.ammo-oracle.com

Really? It is a lot of good info, but I couldn't find an answer to my question. If it is indeed there would you mind to be so kind to post it?:)

Shoot-it
02-09-2006, 10:01 PM
Why does it matter twist rates has too do with bullet weights not how fast they will wear out.

ocabj
02-09-2006, 11:18 PM
Really? It is a lot of good info, but I couldn't find an answer to my question. If it is indeed there would you mind to be so kind to post it?:)

Take the time to read the FAQ.

If you had gone through it, you would have found this -> http://www.ammo-oracle.com/body.htm#wear

Shoot-It is correct. Twist means nothing. You need to understand that barrel life is mainly determined by throat wear. Everytime you fire a round in a gun, the throat takes the brunt of the burning gases, and wears away material in the throat. As the throat wears away, accuracy will be affected. This can be countered by seating the higher within limits of the firearm.

Just be sure to get a chrome lined barrel and you will have a barrel that will last you several thousands of rounds.

scott.cr
02-09-2006, 11:25 PM
Barrel wear can also be countered by using slower ammo (in terms of bullet velocity). Wear is caused by the obvious bullet traveling down the barrel, but is exascerbated by heat. Heat can cause a few microns of the barrel bore's steel to anneal (go to soft state) and this annealed steel is what gets peeled out along with the bullet. The cooler the shot, the less steel is annealed and thus the less wear per shot.

chickenfried
02-09-2006, 11:50 PM
I don't know anything about this stuff. But from ocabj's own ammo oracle link Match rifles often have tighter twists (and therefore more friction or wear) than non-match rifles.

BigAL
02-10-2006, 6:54 AM
The throat will almost always be the first thing to go. How long it takes for this to happen is largely dependent on the type of shooting you do and not barrel twist. Shoot a lot of rapid fire and get the gun hot? It'll wear faster. Shoot a few rounds and let it cool down? It'll last longer. Have chrome lining? It'll last longer. If you can afford enough ammo to wear out a barrel then you will have no problem affording another barrel.

ETA: I recall a post from Bigbore of ADCO on Arfcom who showed pics of a match gun with a throat erosion gauge when new and after several thousand rounds. The difference was dramatic.

mblat
02-10-2006, 8:06 AM
K, admittedly I am no expert, but let me tell you where I see problem with whole ammo-oracle take on the twist thing.

1. It looks that answer to my question is: “Twist doesn’t make a bit of a difference when it comes to barrel life”.
2. Answer to “What twist do I want on my rifle?” is “1x9 probably”


Those 2 statements don’t go together. It seems to me that correct answer is “1x7, but mind that it MAY limit your ability to shoot ultra-light loads, that you probably don’t want to shoot anyway”.

Besides, rumor (if it is rumor) that faster twist means shorter barrel life originated somewhere. I heard and read it many times in many places. What is the source for that?


Regardless: thank you all for answers - now I am convinced that I should buy 1x7 twist.

ocabj
02-10-2006, 8:09 AM
Regardless: thank you all for answers - now I am convinced that I should buy 1x7 twist.

Good choice. All my Colts are 1 in 7. The MK12 Mod1 upper I just received from Adco is 1 in 7.

You will have no problem shooting 55gr and up with the 1 in 7 twist barrel.

BigAL
02-10-2006, 8:12 AM
No problems with 55 grain in my 1/7 either. And it gives you the option of shooting the heavy match stuff too.

6172crew
02-10-2006, 8:15 AM
GI issue is 1x7, thats enough for me.:D

NRAhighpowershooter
02-10-2006, 8:18 AM
Chromed lined barrels will last anywhere from 10K rounds up to and maybe past 30K rounds... Chrome Molly barrels will last approx. 10K - 15K rounds SS match barrels usually get changed out by match shooters after 5K rounds but they will last to about 7K rounds... Just a note on chromed line barrels.. my
M1A that I used as a match rifle had a new GI TRW barrel on it.. I shot it for 5 years in HP practice and matches.. I ran about 18K rounds throught it.. I have since retired that rifle and it will still hold the 10 ring at 200yds with M80 ammo... My HK-91 has about 13K rounds through it and it too will hold the 10 ring at 200yds....