I know .300 BlackOut's are quiet...I'm just not totally sold on the idea for my own personal needs. Buying new dies...finding or making brass...finding projectiles and powder...between having 5.56 and .308, I personally don't need to merge the two calibers.
I've loaded some pretty quiet .308 loads for my Remington 700 with some Trail Boss...using some 150gr Hornady FMJs but I'm looking at getting some 170gr .30-30 round nose bullets for less velocity deviation and more stability at lower speeds.
[video=youtube;eGIqDE2EL-Q]https://www.youtube.com/watch?v=eGIqDE2EL-Q[/video]
The first round went supersonic, I think...10.0gr of TB was a tad too much. 9.5gr sounded a lot better. 5 MILs holdover at 100 yards (18" of drop). Grouping wasn't horrible...probably 1.5-2" inches. I could do better with it if I'd had a reference point on the target and was shooting for precision rather than just marveling at the quiet.