AR Barrel twist/life question. Need difference quantified.

[arthurcw]

Ok... one more stupid AR-15 barrel question. This one is not my fault. In listing all the pros and cons of various AR uppers to my wife, I mentioned that the 1/7 twist rate wears a barrel down faster. So, of course, she asked, “How much faster,” to which I really didn’t have an answer.

I’ve Googled and Asked and I can indeed find that they DO wear faster, but nothing really says HOW MUCH faster. I realize barrel life depends on a number of issues, but assuming we had 2 barrels, one in 1/9, the other in 1/7, and all other things being equal (no beta “C” mag dumps, good ammo, good maintenance and care, chrome lined); how many more rounds should one expect the 1/9 to last?

Now let’s make it harder. Let’s make a something else not equal. Let’s take 2 barrels. One in 1/7 with 4150 steel and the other a 1/9 done up in 4140 steel. Does the harder steel allow this 1/7 to keep pace or at least narrow the gap in life expectancy?

Now the real world application for this question is on the upper we want for our (read her) AR. One is a CMMG (1/7 light weight) and the other is a RRA (1/9 light weight). I’m good with the 1/7, but the Mrs. Is partial to the RRA and barrel life is the reason she is giving. If the softer steel washes any real world life out of the deal, I’m pushing for the 1/7. However, if barrel life is gonna be substantially greater with the 1/9 even with softer steel then I’ll get that one, wait the 12 extra weeks, and make the Mrs. Happy.

Thank you for your time and I promise; No more AR barrel questions. Really. Honest. …sort of.

Anywhooo… the question must be answered before I can proceed. If anyone is married to a redhead, you’ll understand. I keep forgetting to post this and last nights 1/7 thread reminded me I need to get a satisfactory answer so I can move on and buy the <censored> thing already. :banghead:

 

[cracked butt]

It depends on what you are going to use it for and what you consider 'worn out.' A competitor with a 1:7 twist barrel might get 3000-4000
rounds down the pipe before its considered 'worn out' and is removed for a replacement. That 'worn out' barrel will probably still shoot more accurately than a brand new chromed 1:9 barrel but might not function as well with a wide variety of ammo as the chromed barrel..

I would just buy whatever you need, shoot it until it craps out, then replace it. In the grand scheme of things, the cost of a barrel is pretty small compare to the cost of ammo it takes to wear it out.

 

[TexasRifleman]

I would just buy whatever you need, shoot it until it craps out, then replace it. In the grand scheme of things, the cost of a barrel is pretty small compare to the cost of ammo it takes to wear it out.

I think that's the best answer to this. I would never choose a barrel with the prime factor being how fast it might or might not wear out.

Choose what shoots best for your application and deal with it when it wears.

As we know from the other thread yesterday there's not likely to be a straight answer to these questions

 

[arthurcw]

As we know from the other thread yesterday there's not likely to be a straight answer to these questions

WAG's, SWAG's, Guestimations as all ok. I gave up on straight answers a long time ago. This is an AR question, it's like asking for the best way to impress a woman.

 

[Tarvis]

The problem is there are many factors that play into barrel life, and different stages of barrel life as well. From the sound of it, you probably won't have any problems until 15,000 round, possibly even more with either barrel. Maybe the 1-7 lasts 3000 rounds fewer than the 1-9, but how many rounds are you shooting a year? If it's in the 2000 range that's 7 years until you may start to see "wild" accuracy, in which case you can get a new barrel for, say $350. Meanwhile, if you reloaded 15,000 rounds for .25 per round you spent $3750 in ammo. Barrel life is not an issue.

 

[Bartholomew Roberts]

I replaced my 16" chrome-lined 1:9 Bushy HBAR at about 9k rounds after I had difficulty hitting 8" steel at 300yds and IDPA targets at 500yds. The barrel continued to do well at less than 200yds though.

However, I was having no trouble at 600yds with the same ammo/barrel at 7,871rds - so part of me suspects some of the chrome lining flaking off or some other problem with the barrel. I sold it off used on the AR15.com forum and the new owner was happy with it so who knows?

 

[Onmilo]

I believe cracked butt summed it up best.

If you aren't shooting full auto and you aren't shooting as a competitor in 600-1000 meter matches and you normally shoot at 200 meters or less and you normally shoot 100 rounds a month, your barrel is going to provide good service and respectable groups for your forseeable lifetime.
Pick a twist rate that will best suit the bullet weight you will most often use.

For general shooting I like a 1-9 twist, 5.56 NATO chambered, chrome lined barrel.

 

[Bartkowski]

I don't know how much longer it will be, but I would assume that it is not enough to worry about. And between RRA and CMMG I would go with the CMMG. I have seen them both at the same price, and while they are both quality guns, the CMMG didn't cut as many corners.

 

[JesseL]

Pure speculation here:

Part of the perceived difference could be resulting from the types of bullets typically used with different barrel twists.

The longer heavier bullets used in the tighter twist barrels have more bearing surface to wear, and their greater mass tends to push pressures higher.

 

[arthurcw]

Thanks.

Now all I have to do is face the redhead's "Brown Eyes of the Inquisition" one last time.

thanks again.

 

[George Bruce]

I hope I live long enough to wear out my rifle barrels.

 

[dakotasin]

so... your wife wants an ar-15 - or is at least signing off on one - and you want to pick nits over something that, in real world applications, isn't likely to be an issue...?

in all seriousness... not many people wear out a barrel, and, especially on ar-15's, barrels are easy and cheap to come by (even custom/semi-custom pipes). further, 223 barrels have a pretty long life expectancy.

it does not sound like you or your wife have any real strong opinions either way, so the thing to do is to look for another factor to base your purchase on (feel, brand, etc etc).

best of luck... you'll be satisfied either way.

and no, i do not have a solid, concrete answer for you.