re: Official AR-15 thread

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1:9 twist barrels which will stabilize 75gr OTM's just fine.

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Personally, I think that 1:8 and 1:9 twist rates are probably "more versatile" and if a shooter knows he's going to be shooting a wide range of bullet weights, 1:9 might be the right twist rate. Heck, my EA-15 has a moly-chrome barrel with a 1:9 and shoots just fine.

But, the market is providing 1:7 and, unless the shooter is going to shoot a bunch of light bullets through it, that twist rate will not be detrimental to shooting (and, really, with 14.5" and 16" barrels dominating this segment as well, I'm not even sure if you'll get that many problems or all that much increased wear if you shoot some lighter bullets, to be completely frank about it.)

1:8 and 1:9 are probably more versatile barrels and will likely last longer, all other things being equal. Still nothing wrong with a 1:7 in a carbine, though.

You sure you got that right.

A 7 twist would be the most versatile seeing as it can stabilize the widest range of bullets. Your not going to have issues "over stabilizing" espcially in a 223/556. Your run in to problems with a fast twist 22-250 shooting 40gr bullets at 4500fps maybe.

I'd say a 7 twist is the most versatile, but my non scientific guess would be that 98% of ar shooter will never have any idea what we are talking about.

You really needed a book to tell you that?

Cool.

Have you read any of these books?

LINK

I need to get another one.

Not really, too much sugar for these old eyes.

300m is about the best I can do anymore, with iron sights.

Eyes got so bad I sold, up north, my pre-ban SA M1A, all USGI (except, obviously, the receiver).

Sold my pre-ban Colt, PWA & Bushmaster up north, too & replaced them with new ones for less.

Since then, the new ones were all lost, in a terrible accident, deep in the River...

I have witnessed too much twist with too high velocity. 55gr ballistic tip through my 1:8 18" broke apart at around 50yds. I know this because I was shooting over dry dirt and saw the pieces hit dirt and throw dust.

I do wonder if ballistic tips are just more touchy to the twist/velocity/grain ratio then a copper jacketed bullet?

Looking at a Colt 6920 for a starter my guy says he can't get them right now from his buyer, anyone know where I can get one and mabe get it shipped to him?

Various Army Research Laboratory documents and research going back as far as the early days of testing the AR15 rifle. The Army and Navy have done a lot of research and testing and I'm not talking about the crude range tests magazines and professional shooters are limited to, talking about calibrated test equipment and instrumented ranges where everything from the temperature of the ammo (from documented lots) to conditioning of the rifles and measuring bore wear at regular round counts. When the Army was in the process of moving away from M193 and A1 rifles there was a lot of input across the branches and a lot of testing of barrel profiles, twist rates, and ammo types. The DoD does a lot more testing and evaluation of its small arms than most know or will give it credit for.

Being a retired Army Officer, I am aware of such, will have to look into your statements.

Have 3 friends who go to Aberdeen 2-3 times a year; perhaps they may help.

Yes, I'm well aware of that, had some M855 & M856 loaded in my mags, before the accident.