>>61
.300 blk is in term of ballistics just 7.62x39 that fits into AR mags. The bigger caliber and the weigh makes it more suitable for deer hunting than 5.56. But you also gotta consider the price, 5.56 is probably a lot cheaper if most of what you're gonna be doing is shooing for fun/competition. If hunting represents a smaller part of your overall usage it might be best to go with 5.56. Just more options for ammo and it's cheaper and it can still do the job. And check your local laws, some states and region have restrictions on the use of semi auto firearms for hunting and minimum caliber requirements for certain game animals