PDA

View Full Version : Best Bullet weight for AR 1/7 and 1/9 twist?


alex45auto
01-09-2011, 3:33 PM
What bullet weight would be best to use for AR .223 or 5.56 1/7 and 1/9 twist? What effect would using 55 gr and 62 gr bullet have on either twist rate?

1lostinspace
01-09-2011, 3:44 PM
For 1:7 77SMK for 1:9 69SMK

Both will stabilize 55-62gr

killshot44
01-09-2011, 4:52 PM
Oh, man, here we go again.......
Seriously, do a simple search for "twist rate" over in Centerfire Rifles and you'll read all the opinions; some substantiated, some not.

The 1/9 works great to 69gr and, in a true .223 chamber, it may even shoot 75s.
The 1/7 NATO-twist was intended for shooting very long tracer projectiles and to stabilize bullets in extremely cold weather.

The best? It depends on what you'll shoot. The most versatile?, definitely 1/8. But that's uncommon is 16"ers.

BigBronco
01-09-2011, 5:41 PM
So I feed my 1 in 9 mostly 55's. If I wanted to load some match grade target rounds. What bullet is recommended?

Rock6.3
01-09-2011, 5:54 PM
So I feed my 1 in 9 mostly 55's. If I wanted to load some match grade target rounds. What bullet is recommended?

At short distances 55gr will be sufficient.
Wind + 300 yards? A heavier projectile with a better ballistic coefficient will yield better results. Technically a 1:9 twist should be able to stabilize up to 69 grains.

stphnman20
01-09-2011, 5:57 PM
My 1:8 will eat anything from 55gr up to 77gr.. It's love 69gr smk.

GeoffLinder
01-09-2011, 7:12 PM
1:7 and 1:9 (1:8 also) are all pretty much guaranteed to do well with 55gr through 69-70gr bullets. Many 1:9 barrels will stabilize 77gr, but not always, just have to test and see. heavier than 77gr need 1:8 or 1:7 twist barrel to stabilize properly.

The fact to remember here is that you do not need to specifically shoot 77's in a 1:7 and 55 in a 1:9. The real truth here is you just need to find a bullet type and bullet weight that your barrel likes.

The Hornady bulk 55gr FMJBT (Full Metal Jacket Boat Tail) that are available here have shot well in every AR I have (1:7, 1:8 and 1:9 twists).

http://www.midwayusa.com/viewProduct/default.aspx?productNumber=1165165907


If you want a bullet that will almost certainly perform well in 1:7 and in 1:9 then don't look any further than the Sierra SMK69 or the Hornady 68 grain HPBT. Both are pricey but both are good bullets.

Try the Hornady 55gr FMJBT first and if they shoot well in both barrels you can just stop there. I would not hesitate to shoot these in wind out to 300+ meters if need be. I won a practical rifle stage at a regional 3gun match with the Hornady 55gr FMJBT shooting falling steel at 250-300 yards in a 15-20 MPH wind a few years back. They are very good match grade bullets if you aren't trying to print benchrest style bughole groups and can get by with basic MOA performance. Being a boat tail they handle wind very well if you push them 3100fps or better.

The most important thing to do is not just try a specific bullet, but to also test that bullet through each rifle at a range of velocities and look for a velocity that provides the smallest group size in THAT rifle if you are looking at best accuracy.

IME, the Hornady will hold near or at MOA over most any charge weight of any good .223 power in most any AR IF that rifle is capable of holding MOA in the first place.

MTG Firearms
01-09-2011, 8:22 PM
I agree with Geoff. I have four rifles with twist rates being 1 @ 1:9, 2 @ 1:7 and one in 1:8 and they all shoot the 55 gr hornady fmjbt reloads really well. My long range load is a SMK 77 grain and the best results are achieved with 1:7 and 1:8 twist rate.