Training vs. Real world use needs thought.

I'm up in Maine, semi-rural. I'm likely NEVER going to be taking a shot past 150m/yds. Shooting long is fun, but its a different animal than being proficient at "danger close" distances.

Any decent ar15 can hit steel at 600yds. You'll want at least an 18" barrel for that, though. I stick with 16" barrels, a supressor ready flash hider, and M193 556.

300AAC/BLK is very useful. It's better for hog and arguably human hunting, but it costs a lot more, to the point where I'd recommend getting a 556 AR to start, get training, then eventually branch out. For me, I'm just building a 308 "AR10" as that's still cheaper than a 300BLK for regular ammo and much more effective than 300Blk unless you are close in, short barrel length, and suppressed.