I'm going to build an AR, this will be a SHTF/HD rifle as well as hopefully something that's just fun to shoot.
I know the difference between 5.56 and .223 and I would go with a 556 chambering if I use the smaller caliber round.
What I'm curious about it building an AR chambered in something bigger, like .308 (which is also 7.62x51 right?).
Would I have to find a special lower or can I use one marked "multi" and build/buy a .308 upper?
Also if I went that way could I build/buy another upper chambered in 5.56 and simply swap them out on a whim? What about .22lr?
I know the 5.56 is a decent cartridge, but if I'm going to use it as a man/zombie stopper I'd prefer a bigger round. What do y'all think?