Recommendations for 14.5" 1/7 5.56 NATO?

Selectedmarksman · Post by **Selectedmarksman** » Wed Nov 05, 2008 2:11 am

I'm considering buying some ammo in bulk, while we still can and before prices go up. Any recommendations on the best weight to go with for an AR-15 with 14.5" 1/7 twist barrel and 5.56 NATO chambering? It's one of CMMG's perm-attach models with the YHM Phantom flash hider.

I haven't had a chance to test a lot of different loads through it so I thought I'd consult the experts. Thanks in advance!

steve7478 · Post by **steve7478** » Sun Nov 23, 2008 4:36 am

With such a fast twist you can go heavy. Like 70 grains heavy or more even. The 14 inch barrel was given such a fast twist because the bullet needs to kill with expansion instead of yaw. The lighter bullets with a slower twist like the 1:12 with a 20â€

Selectedmarksman · Post by **Selectedmarksman** » Sun Nov 23, 2008 11:04 pm

Outstanding info, thanks Steve7478. I think I will give CMMG a call, they were great during the purchase process.

steve7478 · Post by **steve7478** » Sun Nov 23, 2008 11:47 pm

I have purchased 2 AR's from them and they are very cool. I am trying to talk the wife into going to their next shoot. They are only a few hours drive from my 10-20.

FA Gunner · Post by **FA Gunner** » Tue Nov 25, 2008 10:25 am

Current M-4s are 1-7 twist with a 14.5' barrel. The M16A2 has a 1-7 twist with a 20' barrel. The M16A1 has a 1-12 twist with a 20' barrel. (Some of the earliest were 1-14). 1-9 is a commerical offering, not a US military standard. We went to a faster twist because we went to a heavier bullet.

If you arent using light weight varmint bullets, but regular 55 grs FMJs they should also shoot fine in the 1-7. If you are going to try hollow point varmint type loads then you will probably need a slower twist, since you might get jacket seperation with these lightweight varmint bullets. Also if you are looking at shooting the heavier tracer rounds they should only be used in faster twist rifles since they are longer. The length of the bullet is what generally determines the twist that it needs. A longer bullet needs a faster twist to stablize in flight. A shorter bullet can use a slower twist. This why the commercial offering is generally 1-9 or 1-8, it is a comprimise.

The 62 grain M855 and any other FMJ doesnt expand at all, no matter the twist rate. 55 grains dont readily tumble in the target in either twist rate with a short barrel, it is velocity that causes them to do this and then fragment. With the 14.5 barrel length you dont get enough muzzle velocity to tumble in the target with either bullet out past certain distances (I cant recall the approximate distance, you check out the ammo oracle over on AR-15.com for it). This why everyone complains about the M-4, all you do is put small holes in your target, unless you hit a bone you dont get any tumbling.

steve7478 · Post by **steve7478** » Tue Nov 25, 2008 12:46 pm

I know that m193 and m855 are not expanding bullets. I was told that in the short fast barrels it was better to use other types that expand because they canâ€™t gain enough speed to tumble. Thanks for the clarification on the M-4.

FA Gunner · Post by **FA Gunner** » Tue Nov 25, 2008 3:03 pm

Steve, i got confused on what you were saying in your post. Your right about the expanding bullets being better ones to use, I wish I could have some right now, but I am stuck carrying the basic M855 stuff. Luckily I got rid of the british stuff that they first issued me when I got in country. It doesnt have the right burn rate and caused jams in my M-4.

I am also trying to figure out what bullet is to be my primary load. I am not a fan of FMJs unless my target has some kind of protection and I need penetration. But right now it is all academic for the next 6 months until I get back home.

Marksman, let us know what you find that works best for you.

Also here is the link for the ammo oracle over on ar-15.com, with alot of good info on 556/223 ammo. http://ammo.ar15.com/ammo/

steve7478 · Post by **steve7478** » Tue Nov 25, 2008 4:51 pm

I hear TAP is the s--t to have on hand here stateside for the 1:9's. I was not born in a golden palace with a ruby and gem covered crib so I shoot what I can afford. I shoot a lot of m193 out of my 10.5'' 1:12 A1. I have 2 1:9â€™s that shoot anything I feed it. The impact points are a little different depending on the different types of ammo used, but the accuracy out to 200 yards is about the same. (canâ€™t take any longer shots around here). I donâ€™t have a SHTF stash. I figure what I donâ€™t do with ballistics I will make up for in volume. If you have a 14.5 with a 1:7 and Uncle Sam is handing you 62gn M855 to send downrange what is your $0.02 on that combo? I kinda get that you are not a fan but what is the range at which it becomes ineffective and how is accuracy?

FA Gunner · Post by **FA Gunner** » Tue Nov 25, 2008 11:36 pm

I am going to try the TAP when I get back, but like you I cant afford very much of it. Mainly I use the M193, as I shoot that I am going to break out my reloading bench to make up something along the lines of the TAP.

The M855 is accurate enough, never printed it, but at the zero range (25M) can get 3 rounds into about 1/2" with a M-4 and ACOG so figure that means about 2-3" at 100 yards. The problem is the terminal ballistics, most of the time I have seen it just punch a 22 dia hole in the target. Dont get me wrong we are putting guys down with it from point blank out to 200 to 300m here in Afghanistan, but you have to have shot placement to take them down quickly. There are some newer loads that the military is using for some of the units, but all I have ever seen or shot is the basic M855 stuff.

I cant say at what range they tumble and what range they dont. They throw some ranges out over on the ammo oracle but those can always be debated. I think there are better bullets out there now that can give us the penetration that we need while at the same time giving us expansion too, just dont know which ones they are.