The cartridge started out as a wildcat called the 300 Whisper. I think SSK (J D Jones) had it CIP standardized long before AAC renamed and got a SAMMI standard as 300 Blackout.
I've used the round in a bolt action rifle for shooting feral hogs and a few deer. Loaded with a 110gr or 125gr bullet you can duplicate 7.62x39 ballistics easily. Where the 300 BLK shines is with heavy bullet subsonic loads with a suppressor. I load a Hornady 190 Sub-X FTX to 1025fps, the bullet expands consistently on hits out to about 60 yards. That load is used at night, suppressed with a night vision scope for killing feral hogs.
Thank you for your precise and informative answer.
Just for your information: In Germany the 7,62x39 is allowed only for hunting roes, foxes or other smaller animals, so called small game.
If you hunt heavier animals - so called big game (feral hogs, fellow deer, red deer) - we have the legal rule, that the caliber must be at least 6.5 mm (~ 0.255 inch) and the impact energy at 100 m (E100) must be at least 2000 joules.
Normal 7,62x39 cartridges don't reach that impact energy at 100 m.
So if someone wants to use in Germany for example 300 Blackout for big game, he has to prove by an official test, that it reaches the 2000 joules. As long as that isn't proved, no arms dealer will offer any rifle in 300 Blackout here.
Whether such a law as in Germany with a prescribed impact energy is good or bad may remain open. It certainly has advantages and disadvantages.
But I wish you always good hunting (in Germany we say "Waidmannsheil" or "Weidmannsheil") with your rifle in caliber 300 Blackout. 
Those rules seem a bit arbitrary, the 250 Savage and 243 Winchester generate more than the minimum required energy and are well proven on game. My preferred medium game cartrideges are 243 and 25-06. Humanely harvested a lot of Whitetail, Mule, and Axis deer with those rounds.
Here in Texas hogs are an invasive non-game animal and can be shot with any cartridge or destroyed by any means that doesn't endanger native game animals. I trap, poison or shoot, any I see on the family land. One of the larger ranches in the area charges hunters a fee to take them. Those morons are a large part of the problem. All of the other ranches and farms allow free, controlled access to responsible hunters. One of the favorite rounds used is .223/5.56, not my first choice, but, works well enough with proper shot placement. I've probably killed the most with a 357 magnum lever action carbine or 7.62x39 bolt action. Those are the rifles that get carried most of the time, I'm out walking or in the truck checking fences.
