AR-15 1:8 twist...The best?


April 18, 2010, 09:43 AM
I know 1:7 is "the rage" due to being mil-spec, but I find it to be a liability if you plan on using your AR for anything more than home defense. The lower 50 and 44 grain ammo is the most common around these parts, and the 1:7 seems to have a bad reputation for accuracy with these grains. At the same time, the 1:9 doesn't handle the high grain defense loads well.

So, what about the 1:8? What kind of grain range is usable accurately in a 1:8 twist? Is it good for accuracy, or a twist rate that does everything good and nothing excellently?

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Bartholomew Roberts
April 18, 2010, 10:07 AM
I have a 1:8 and a 1:7, so far I have not found any load that the 1:7 will handle that the 1:8 will not and vice versa. The lightest I've shot is WWB 45gr JHP and the longest is 77gr Mk262 Mod 0.

April 18, 2010, 10:43 AM
My opinion is that 1:8 is pretty much ideal for common modern bullet weights (55-77gr) used by most of us, and I wish it was more readily available. 1:7 is faster than needed if you aren't using 80gr+ and 1:9 of course is marginal for 75-77gr. Unfortunately it seems that 1:8 is readily available only in stainless barrels, at the moment.

April 18, 2010, 10:45 AM
I've shot 80 grain loads on across the course matches out of my RRA with a 1 x 8 and it functioned fine. The only bullet I could think of would be the Sierra MK 90 grain that MIGHT prefer a 1 x 7. But they are a match only load, as is the 80 grain.

Uncle Mike
April 18, 2010, 11:55 AM
Until you get to 200y-300y you are NOT going to see any difference between a 1/7, 1/8 and 1/9 with anything factory loaded!

Don't sweat it, if you are going to be using 55gr. or less, then ANY of those twists will do you well, I would lean towards the slower twist if you plan on a steady 40, 45 grain diet, if on the other hand you intend to shoot for groups at distance, well, you'll have to match the twist to the bullet(s) you intend to use.

Al LaVodka
April 18, 2010, 12:50 PM
This is not rocket science tho some people try to make it such it has seemed to me, and Rambos have their "if the Army does it" simple-minded philosophy...

Are you really going to shoot European 62 gr. to 77 gr. military incendiary tracer or compete in 1,000 yard target competition with 80 grain rounds that won't fit in a magazine if loaded properly? If not the answer is stay away from 1:7 grain. Duh.

Are you basically ONLY going to shoot 62 gr. NATO? If the answer is still no, stay away from 1:8.

Are you going to shoot UP TO 62 gr. NATO? If the answer is now yes get 1:9 (tho 1:8 is still better than the over-compensating 1:7 industry-foisted fad).

If u r basically never going to shoot even as heavy as 62 gr., which is fairly common, get a 1:11.


Bartholomew Roberts
April 18, 2010, 01:04 PM
The only thing you lose by using a 1:7 twist is the ability to shoot really thin-skinned varmint rounds lighter than 45gr. Everything else works just fine in a 1:7 twist with good practical accuracy. For varminting, you may want to look at a 1:9, though I think a 1:12 is overkill. Since I don't have any desire to shoot rounds lighter than 45gr, either 1:8 or 1:7 will shoot any round I could conceivably want to use.

For reference:

April 18, 2010, 01:35 PM
You'll probably be happy with a 1:8

Select a twist rate that is generally compatible with the bullet you intend to shoot, and then buy the very best barrel you can afford.

I'd rather have a quality barrel of the "wrong" twist rate, than a crummy barrel of the "right" twist rate.

April 18, 2010, 09:52 PM
I have two ar's with 1:8 twist in 18" and 24" and they shoot anything up to 77gr. excellently. My 1:9 16" barrel shoots very good up to 69gr.

Welding Rod
April 18, 2010, 10:35 PM
My Rock River 20" SS 1:8 HBAR seems to like 75 grain TAP, and 69 grain FGMM. It has put both sub MOA (5 shots) to 500 yards. Best 5 shot group at 500 was just under 3/4 MOA with 75 grain TAP FPD.

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