I’ve got a chance to aquire an unfired AR15 at a great price (motivated seller). I’ll just say it’s a top maker. The only problem I have is the rifle has a chrome moly, non-chrome lined, 1/9 twist barrel. Having read all of the recommendation threads I’m a little paranoid to buy it.
What exactly can I expect from a non-chrome lined 1/9?
Thanks.
I am guessing that it may be a 6721? If so they are great rifles. I have one, but sold the factory barrel, form 1’ed it and put a 12.5 noveske on it. If you can acquire the for a good price, even if it isn’t a 6721, you can sell the barrel and get you a good Midlenght 16" barrel such as Noveske’s and you will have a damn fine rifle. But to be honest with you, unless you will be using the rifle in extremely harsh conditions, you will probably be fine with the barrel that is on that rifle.
I’d like to keep it a bargain, thus keeping it as is. The barrel swap expense would still make it a great buy … but what if I just kept it as is? The way people talk the barrel will explode on me, or it will fail me somehow because it is non-chrome lined and 1/9?
It being a 1/9 twist , the longer bullets may/may not stabilize that well. Thi is especially true of tracers, They will exhibit irratic flight around 200-300 yards. The crome lined 1/7 twist is mil-spec, and the crome lining is a good thing to have in a field use gun. If you are just training/plinking with this rifle and not taking it to war, you should be fine, in my opinion.
Steal the deal! My 1:9 M&P-15 is reasonably accurate with 77gr Black Hills and 75gr overlength Hornady AMAX handloads that won’t fit in the mag and have to be fed one at a time. The only way to find out is to test-fire the rounds you want to use. If they function and group well, then there’s no need for another barrel until you wear that one out. If they don’t, then the worst that can happen is you then get to buy the barrel you want.
you do allot of competition?
If it’s really a bargain than it’s a bargain - buy it, shoot it until the barrel goes south, then re-barrel. Then repeat that sequence several more times. 
I have a Colt 1/9 non chromed bore, I usually shoot 50 gr bullets for coyotes. It’s plenty accurate and I don’t worry about cleaning it much. I’ve hunted all day in the rain during a contest and it didn’t “explode”.
I’ve seen several of those Colt’s and they tend to shoot well. Mine does shoot 77 grain bullets almost as well as my 1/8 twist Kreiger RECCE.
I thought the 6721 had a chrome lined barrel. Am I wrong?
I’m certainly no expert but the 6721 I had came with a chrome lined barrel.
Not as much as I should. The 75 AMAXes are for my match rifle, a DPMS DCM, and I have hit as many as six Xs in a 20-shot match at 600 yards, so the 1:8 twist in the match rifle is getting it done. One day I shot a few of those loads through my carbine. They grouped as well as anything, with no signs of keyholing at 150 yards. 1:8 and 1:9 twist seem to do fine, although as others have pointed out, they might not be exactly 8 or 9" between twists. Where you need 1:7 or 1:6.5 might be for the super-long 90gr match bullets. When my match AR needs a new barrel, that’s what I’ll go to.
I think the 6721 has a chrome chamber, but I don’t think the barrel is chromed. I could very well be wrong though.
Specifications:
Caliber: .223 Remington (5.56mm)
Magazine: 2 20-round LE mags
Weight: 7 lbs
Length-stock retracted: 32 inches
Length-stock extended: 35 inches
Barrel: 16 inches, Chrome Lined
Twist: 1 in 9 RH
Finish: Black Anodized / Manganese phosphate
Item Number: Colt AR6721
Code 4 website.
I have a Colt (Competition Match HBAR II) from the mid 1990s with a non-chrome lined 16 inch HBAR with 1-in-9 twist. I don’t lose any sleep over the non-chrome lined part. It shoots Black Hills 68gr OTM blue box well. I have a box of the 75gr OTM that I’ll probably try in the spring.