What Bullet Grain Do You Prefer?

[Abraham]

So far, I've only shot 5.56/55 grain and 62 grain.

I'm told my accuracy, which is fair, will greatly improve with a heavier grain bullet in a 7:1 twist colt 16" AR barrel.

I'm looking at 77 grain 5.56 Magtech/CBC. They're priced somewhat reasonably for what they are.

Of course, the problem with heavier bullets is cost. Once you get past 55 or 62 grain the cost skyrockets.

What grain bullet in your 7:1 AR do you prefer for increased accuracy?

[Richbirdhunter]

I shoot a 77gr in my 1:7 twist but I hand load so that helps

[Pawpaw]

My 16" pencil barreled Colt is most accurate with Fiocchi 77 gr SMK.

With that ammo, I can repeatedly hit a 6 or 8" plate at 500 yards. This with only a 4x ACOG.

[Abraham]

AndyC,

1/7 55-85 grains

1/9 45-75 grains

I'm still learning...maybe I'll buy a 1:9 twist rate barrel, maybe...maybe not.

That said, I get decent accuracy, but not competition accuracy with 55 or 62 grain bullets, it's just that I'd like to see if a heavier bullet weight really makes that much difference.

If yes, then the likely hood of me getting a 1:9 barrel may become a reality.

[Pawpaw]

Boy, I'm sure glad I specifically bought a 1-9" twist so I don't have to fret over expensive bullets

Surprisingly, that same rifle will shoot 2 to 2.5 MOA at 100 yards with 50gr Federal tipped varmint ammo.

http://www.midwayusa.com/product/953830 ... uctFinding

[ShootDontTalk]

My NRA High Power Service Rifle gun will shoot any length bullet. Anything over magazine length must be loaded one round at a time though. I have not found any factory loaded round that performs as well as Black Hills 77 grain match. It is more expensive but delivers 1/2 MOA out to 600 yards from a bench and 3/4 to 1 MOA in competition when wind is not a factor. Heavier bullet hand loads will do better in the wind.

For home defense I use Winchester 64gr PSP. You can spend more, but all you are getting is better barrier penetration.

[Abraham]

Thanks all for your input and advice.

[ghostrider]

55gr FMJ and win 64gr PP
I have a 1-in-9" bbl, but am building a 1-in-7"

[rbwhatever1]

Boy, I'm sure glad I specifically bought a 1-9" twist so I don't have to fret over expensive bullets

Me too. All of my 223/5.56 rifles have 1-9 twist rates.

[The Annoyed Man]

Boy, I'm sure glad I specifically bought a 1-9" twist so I don't have to fret over expensive bullets

AndyC,

1/7 55-85 grains

1/9 45-75 grains

I'm still learning...maybe I'll buy a 1:9 twist rate barrel, maybe...maybe not.

That said, I get decent accuracy, but not competition accuracy with 55 or 62 grain bullets, it's just that I'd like to see if a heavier bullet weight really makes that much difference.

If yes, then the likely hood of me getting a 1:9 barrel may become a reality.

Both of you should check out this article about M855, because it has some interesting information about bullet weights versus barrel twist rates that I found intriguing. Some of it confirms what I've already believed, and some of it was new to me.

http://www.americanrifleman.org/article ... cartridge/

The interesting factoid..... with 62 grain ball, regardless of whether we are talking about M855 or M855A1, a 1:9 barrel is twice as accurate as a 1:7 — per the Army's testing of both bullets, using both twists. I once spoke with a former QC guy at Lake City about barrel twist and 5.56 ammo. His job was to fire 1000's of rounds every day for batch quality at Lake City Arsenal. He told me the same thing the above article stated - that the 1:7 twist for the M4 was adopted only to accommodate the longer and slightly heavier bullet of tracer ammo. The other NATO members, shooting SS109 (identical to M855 ball), have kept their twist rate at 1:9, with better accuracy.

We often forget that 1:9 is already a much tighter twist than the original 1:12 the M16 deployed with back when 55 grain M193 was the standard bullet.

Personally, I've grown fond of 1:8 for a variety of reasons, but I own two 1:9 barrels, and after reading that article, like AndyC, I don't feel the need to go with 1:7 unless I was going to shoot heavy match ammo exclusively. And I don't knock the AR platform at all......I love it, in fact.......but if I want true match accuracy, I'm going to go with a bolt rifle most of the time anyway. If an AR will shoot 2 MOA reliably with a range of bullet weights, that is good enough performance to get the job done at any distance that I have any business attempting the shot. You have to decide if your AR is a general purpose rifle, or a sniper rifle. If it's a general purpose rifle, 1:9 is just fine.

[SkipB]

Interesting article Annoyed Man. Thanks for posting it.

[ShootDontTalk]

The original prototype M-16's had a 1:14 twist. It was found during military trials that in inclement weather, or other than standard temp/pressure conditions, there was keyholing of the 53-55 grain bullets, thus the 1:12.

Most specialty barrels for ultimate accuracy use either 1:8 or 1:7. The rule of thumb taught by the AMU is choose the twist rate needed for the heaviest bullet you plan to use. They shoot 1:8 or 1:7 barrels. Here is a nutshell of some surprising research on twist rate versus bullet weight using the latest design bullets:

http://weaponsman.com/?p=7291" onclick="window.open(this.href);return false;

My competition Service rifle has a White Oak Armament barrel. Here is the latest from them:

Q: But won’t a 1-7 or 1-8 overspin my bullets?
A: When selecting twist rate it is important to remember that you want to stabilize the heaviest bullet weight you will be shooting and anything lighter will be stabilized. While inaccuracy due to overspinning was a concern in the past, with the higher quality bullets being produced today, a shooter doesn’t need to worry about a light bullet being inaccurate if overspun.

Even though accuracy is not of concern, if shooting a very light bullet at high velocity with a fast twist, it is possible to spin the bullet fast enough for it to come apart before reaching the target. If you will be shooting light bullets exclusively, we recommend a 1-12 twist.

Italics mine. To tell the truth, even when not using the latest bullet designs, I never noticed any change of accuracy from the lightest to the heaviest with 1:8 or 1:7 barrels. I think you could prove that easily. I think I'd choose the faster twist barrel and just shoot whatever you want. You'll be fine.

Key to remember: Short barrels of 14 or less inches need fast (1:8 or 1:7) twists and heavy bullets. Not for accuracy, but because the lighter bullets won't tumble (because of low velocity) and cause maximum wounding potential. 16 inch barrels and up are pretty much a non-issue.

[Abraham]

TAM and SDT,

Thanks for all the great information.