I have always shot handguns but recently started getting more into shooting long guns.

I have a RRA carbine with a 16" barrel (1:9 twist) and a Colt 6920 with a 16" barrel (1:7 twist).

For training/target shooting, which do you recommend, the 55 grain or 62 grain rounds? Will either round work just about the same in either carbine?

Say I sight in the Colt using the 62 grain stuff. Would it be significantly off firing 55 grain stuff then?

Thanks.

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Aaron Terry

Just like shooting hand guns, long guns and ammo preference is trial and error.

As a general rule, the 1:7 twist likes heavier (longer) bullets while the 1:9 twist likes lighter (shorter) bullets.

I always thought that 1:9" was ideal for 62 gr., but stabilizes 55 gr. ammo well, and the military use 1:7" to stabilize the longer M856 (?) tracer. M16A1s which have a 1:12" twist are designed around M193 55 gr. ammo.

+1 for what flopshank said

I think most people train CQB and out to 200m with lead core M193 55gn. It's a little cheeper than 62gn M855/SS109, and it's easier on the plates if you're shooting at steel.

For distance (200m+) 1/9 will work on most stuff to up to 69gn, 1/7 is needed for the 77gn. What your RRA likes best is kinda trial and error. Generally you'll shoot far fewer rounds training for long range than CQB. While it's always best to zero with the ammo you're using, up close the difference between 55gn and 62gn isn't really gonna matter. For 200m+ or patrol use it makes a difference. So if you're training to run and gun the 55gn is fine; for patrol make sure you're zeroed for the ammo you're carrying.

/c

I feel that the 1:9 twist is ideal. Mine shoots everything from 35 gr. Hornet bullets to 62 gr. bullets equally well. It also shoots .223" and .224" bullets equally well. And most important to me, it will stabilize every weight and profile of Barnes X Bullet, ranging from 45 to 62 grs. Obviously some loads will shoot better than others, but I encounter only slight vertical dispersion between the different bullet weights.

Dave Sinko

The 55 grain M193 is better than the 62 grain M855 at everything other than longer range penetration. Within 150 (16") or 200 (20") meters the M193 penetrates and fragments better than the M855. Some 1:9 twist barrels will shoot the heavier 75-77 grain bullets OK and some won't. The Winchester 64 grain PSP bullet is one of the best hunting bullets for larger than varmint sized animals.

m.

Allot of good advice given.

Aaron...If you have any more questions about .223 & 5.56 chick on the link at AR15.com. :: Ammo Oracle Everything thing in the world you ever wanted to know about the ammo should be there.

Good Luck. !

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S&WCA # 2045

All my 5.56 rifles have 1x9" twists. When I was shooting lots of USPSA 3-Gun, I used Federal American Eagle 55gr. ammo for everything but long range stages, and switched to 69gr. Federal Match for the 300 yard work. In the old Eagle Arms Action Master I was shooting then, both loads hit to the same elevation out to about 350 yards, but I had to take 1 min. of windage adjustment (I forget which direction.) when I switched to 69 gr. That rifle groups in 3/4 min. with the AE, and in 1/2 min. with 69 gr. match. I've not gotten very good accuracy with any 62gr. FMJ loads in any of my ARs. Interestingly, while some will tell you that you need 1x8" or faster to stabilize 77gr. bullets, I'm getting great accuracy from my 1x9" ARs with some 77gr. Sierra OTM loads I worked up, duplicating the Mk242Mod 0 loading that is working well in the sand box.

I've shot a lot of 223 and find that a 1-9 twist rate will stabilize all but the longest, heaviest boat-tail match bullets. I'm with 38-44HD45 all the way on this one, I think it's good up through the 77 grain Sierras and is more than adequate for the various 69s. For the 80s it's marginal, but in some guns seems to work okay.