One of the best attributes of the AR platform is that it is so easy to have many flavors of upper run on the same lower. Buy good quality and get a trigger you like and a preferred stock and you can put uppers together for $200-500 all day.
5.56/.223 is great for varmints and target shooting, the military is invested in it fir shooting people (which is different from shooting game) and it will certainly kill deer and pigs. The 6.8spc was designed as an improvement over the 5.56 for mil use, and it is, especially at close engagement ranges, and is deadly on game. 6.8 ammo is easy to find but not a lot of options for projectiles.
7.62x39 is nearly interchangeable with 300blk but needs a distinct bolt and mags, like the 6.8, so you will need separate BCGs for each of those uppers. 300 blk is great within 200 yards especially on tough animals like hogs, with supersonic loads and if you have the coin and want/have a suppressor then a short-barreled pistol or SBR, expanding sub-sonic loads provide a unique challenge for up-close hunting. Then there are the longer range options such as 6.5 Grendel, 270 AR, 7mm Valkyrie, etc.
Last edited by Mdees; 02/04/16 07:50 AM.