The AR-15 concept and design is based on the creation of the 223 from the 222mag for the AR. The original cartridge design was a 55 grain bullet at 3,250 fps to be effective at 300 meters. That is it in a nutshell.
Been an armorer since 1964, 101st Airborne Division, when our M-14s were turned in for XM-16E1s. Twist was a bit off and guys broke the crap out of them, 4-7 per jump, etc, etc. I wrote the reports to the Pentagon on performance, not all glowing, unless you figure in the heated words. Today the ARs are decades improved.
You just buy a 223 AR from one of the better known houses on sale. Sugges a 16" with a medium to heavy 1-8 twist barrel, flat top, chrome molly will do, you wear it out get a better barrel. A flat top upper with a 2 x 7 or better variable scope. A 3# trigger should do fine. The Sierra 53 SMKs with H-335 or 844 or 2023, no N anything is needed or any wazoo, super bullet either.
Hogs and yotes ain't bullet proof.
