I own .300 Blackout. I have the 16 inch barrel with no suppressor. When I first built the rifle, I purchased PNW ammo in 147 grain. The barrel (SI Defense in 1/8 twist) is tuned for only supersonic from the factory. In order to cycle subsonic you would need to open up the gas hole on the barrel to cycle subsonic properly. At first, the rifle had an issue cycling the supersonic rounds. I thought 147grn rounds were too "subsonic" but the issue was I misaligned the gas port and hole. Because of that issue, I purchased some 115grn Remington rounds thinking it was the ammo, not the misalignment. Now this rifle works beautifully with both grains. There is a little more recoil compared to 5.56 but less than .308 . Also, the round is A LOT louder that 5.56. To me, it sounds a lot like a .308 AR, at least using supersonic ammo. I have been waiting till after Christmas to purchase a suppressor for it to test the Decibels of the rounds both super- and subsonic.
The video is correct about a lot of the attributes of the round and the interchangeability of 5.56 ARs and .300 Blackout ARs. Both my metal and PMags fit the round right to a 30 count. Of course, this shouldn't be a total surprise seeing that the .300 brass is essentially 5.56 brass cut and the neck re sized for the larger bullet. Because of this, the bolt is the same. No need for a specialized bolt like many other wildcats. Here is a few pictures of the brass and rifle.
There are a couple of disadvantages to this wildcat, though. One is the availability of ammo for it. Unless you reload, finding it can be a chore. All the shops I have been to don't carry it, making you purchase the ammo online or reloading ammo yourself. Another disadvantage is the "rainbowing" of the round. This round is definitely not a long range shooter. Unfortunately, I have only shot it out to 100 yards with no real bullet drop. However, many articles online have showed that bullet drop can become significant past two hundred yards.
Ultimately, I like the round but hate having to search and wait for ammo. It is a nice difference from a standard AR without breaking your wallet over the price of the rifle, like an AR 10 will. Combined with the ex changeability of parts to the 5.56 AR and the extra "ommpf" from the round, I enjoy shooting it.
Here is a link to more information about the round and the rifles with and without suppressors.
http://300aacblackout.com/resources/300-BLK.pdf