I have a 762X39 upper that I use for hogs. I really like this caliber for hunting. Just the right amount of power for my needs.
Reliable mags are available from ASC, AR Stoner, or C Products. I think they are all made by the same company.
You can reload custom ammo, or do as I do and just replace the fmj bullets with Hornady or Winchester sp hunting bullets if you want to use steel case stuff for hunting.
Make a hole