I currently have a Colt AR-15 A2 Cal .223 Sporter II is the markings on the receiver and on the barrel is stamped CMP 5.56 Nato 1/7 and it is a 20". My question is for a 20" barrel with a 1/7 twist what type of ammo can I shoot? I have put 55gr and some 62gr through it but am curious if I can use some of the other ammo I have heard about like the 52gr, 69gr, 70gr, 72gr, 75gr or 80gr? What is a throated barrel and what is Moly coated does it refer to the barrel or the ammo or both. Also someone told me once that there is a small difference between .223 and 5.56 Nato and that they were not fully interchangeable is this true or wives tale? With a 20" barrel can I expect to shoot 600m and 1000m decently? If so what effect does the twist rate have on its ability to shoot certain gr weights of bullets and at what distances? Thanks for any and all help.

With 80 grain bullets, you will probably have to single load. The overall length is too long. The 5.56 chamber is mil-spec, .223 is (tighter) commercial-spec. Moly-coated bullets supposedly reduce barrel wear and cleaning time. A one in seven twist should be okay for everything you can find to shoot. (Technically, M856/SS110 tracers need a one in five for optimum stability.) See the Ammo FAQ Troy has in the Ammunition Forum for details on the various ammo. Also, there are links to other ammo reviews...

Scott

There are some knowledgeable mofos hanging about the Ammunition Forum:

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