AR Ammo Question?


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tpaw
November 18, 2008, 12:12 AM
Which one for a 1/9 twist AR?

Can anyone recommend the most accepted grain weight and bullet tip (hollow point, FMJ, SP) for a 16" or 18" barrel AR?

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cuervo
November 18, 2008, 12:25 AM
From http://www.triplebreakproducts.com/FAQ/twist_rate_for_barrel.htm

Twist Rate for Barrel?

What is the right twist rate for an AR15/M16 barrel? The below is from Corey Sattler of Olympic Arms. It will give you a good idea of what you should look at.

* 1x7
Technically too tight of a twist for any .224 bullet widely available, including the 80 grain. Manufactured originally to stabilize SS109 and/or tracer ammo, but further military testing has shown other twists to be superior. Some of the very heavy custom stuff (87 grain?) may work well, but why?
* 1x8
Great twist for 69-80 grain bullets. Sierra once informed me that the perfect twist for their 80gr was 1x8.2xxxxx (blah blah blah big long engineers explanation followed).
* 1x9
Good all around twist ratio. Best suited for 52-69 grain, but either end of the envelope will be questionable.
* 1x10
Practically the same as 1x9, but favors the lighter side a little more.
* 1x12
Great for the 40-52 grain bullets. Most often found on bolt action rifles as their primary use is varminting. All right for the 55 grain, but not the best.
* 1x14
If you want to under stabilize the .224 bullet, use this twist. Useless except for tumbling effect it causes upon bullet impact. IMHO, better to shoot straight with a good HP bullet as your chances to hit are better and damage will most likely be greater also.

The bullet type would be more dependent on what you're doing, ie. target shooting (FMJ) or varmint shooting (HP) and what feeds best in your rifle.

ANDROTAZ
November 18, 2008, 12:26 AM
A lot of folks shoot 55 gr out of their 1:9, but it will likely stabilize anything up to 69 or so, maybe a bit more, depending on the weapon. As for defense, I personally just stick with M193 and M855 ball because it's good, affordable ammo and if someone doesn't go down from 5 rounds of 5.56 ball to the chest, I'm effed anyway. This also allows me to shoot the same ammo at the range as I would for SHTF.

Some folks do like to drop some cash on ammo like the Hornady 75 gr TAP or Black Hills OTM...but I just can't justify it. My AR is not for home defense; that's why I have a 12 gauge and handguns. The AR is for SHTF, in which case I want a TON of ammo that I know will go "bang"...and that's the M855.

crazy-mp
November 18, 2008, 12:34 AM
I used to shoot my H-bar quite a bit and my rifle always did better with the 55 gr. HP from Black Hills. I donít shoot that anymore though, mainly because of the price, if you want to do very much shooting look into reloading.

The best ammo for your gun is simple, buy about 5 or 6 different brands of bullets with different weights to start out with and go shoot most of the time, not always but most of the time you can find a good one you like pretty quick.

Hope I could be of some help

gazpacho
November 18, 2008, 04:44 AM
Ammo Oracle (http://ammo.ar15.com/ammo/)

stubbicatt
November 18, 2008, 09:37 AM
Hard to say what your rifle will like until you try to feed it different stuff. Initially what I would recommend is that you buy 20 rounds each, of high quality, match grade, ammunition in the bullet weights you think you are likely to choose from. Shoot the rifle at 200 yards or so to get a good comparison of what it likes and what it doesn't like. You will likely notice a significant accuracy shortfall shooting 75 grain bullets, and shooting 45 grain bullets. There will be a bullet weight which is just the cat's azz. Go with that.

My 2 cents.

SSN Vet
November 18, 2008, 10:46 AM
I'm loading 69 gr. Sierra Match Kings (BTHP) for a 16" 1in9 twist barrel and am getting my best groups ever.

That's the heaviets bullet I've tried in this barrel.

As other have pointed out.....it's not an exact science. If you really want to know if your barrel will stabilize the bullet, you're going to have to buy and shoot some.

Despite the uniformity of modern machining, there are still variables in the geometry of the barrel. They're very, very small variables.....but variable none the less.

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