Has anyone had the pleasure of firing a rifle chambered in either .300 AAC Blackout or .300 Whisperer cartridge? All the things I read online say it's fantastic and may be the next big thing in an AR rifle platform hunting cartridge. The Bullet itself is a 7.62X35 and is supposed to carry more energy than an AK47 Round.It had capabilities of shooting a 105 grain bullet supersonic all the way up to a 220 grain bullet subsonic and can be mated with a suppressor. The word is this rifle with a suppressor is ultra quiet. I am thinking on building an .300 Blackout Upper Receiver and since the folks on here are straight shooters I thought I'd ask and see if there was some feedback from the members.