That sure looks like the silencershop guy.
To be fair inhandloads the 6.8 and 7.62x39 can replicate most of the properties of 300blk and even beat it out in certain areas. Apparently the 308 can too, but I'm wondering what was involved in terms of adjustable gas blocks, buffer springs, etc..
Well, even if he is someone of report, it still isn't commercially available so in my mind it isn't viable. Having said that though, and I guess I should go back and edit the post, none of the vids NWS posted are in AR15/M16 pattern hosts, which is what the 300blk was designed for.
In that platform rifle, only the 6.8 you mentioned would be competition.