'sup guys!
I've been shooting .300 blackout since early this year and love it. If you're trying to decide between the two, keep in mind what you plan to use it for.
100-150 yards - .300 blackout
suppressor - .300 blackout
coyotes - .300 blackout supersonic if distance is an issue
reloading - .300 blackout
catching on - ...dunno...I suck at reading the future
From what I gather you're looking for, .300 blackout seems ideal. 100-150 yards .300 blackout is perfect. As you get to between 200-500 yards, you start to experience a lot of bullet drop. Below that, you're golden. As for suppressor use the .300 blackout is far superior to 6.5 grendel due to the ability to load subsonic. Coyote hunting will be fine with .300 blackout. It's really caught on in Texas for hog hunting using both subsonic and supersonic. Reloading is a no brainer. You can use pretty much any .30 cal bullet for .300 blackout. Brass is plentiful if you form from 5.56 cases. Subsonic loads are relatively gentle on the brass as well. I mainly use only 2 bullets. 175 smk for supersonic which also meets major power factor in IPSC. 220 smk for quiet subsonic loads.
Building your .300 blackout upper is also a breeze. Simply swap barrels. That's it. Same bolt, mags, upper, etc. Only issue I had was my subsonic loads not cycling in my Rainier Arms Match barrel. Easy fix. Enlarge the gas port a smidge and it was good to go. Haven't had a problem since.
I've been extremely happy with .300 blackout. In fact, I shoot it way more than I do 5.56. Mostly because it's more comfortable to shoot with a suppressor.
But not to step on the toes of 6.5 grendel shooters. I have no experience with that round. For what I shoot .300 blackout fit the bill. Have fun!
