For anyone that hasn't heard yet, AAC and Remington have made the .300 whisper concept legitimate with their new .300 BLK (stands for blackout) cartridge. It is saami spec'd and open license. So anyone can use it. [Broken External Image] It's a 5.56 cartridge cut down and necked up to .308 cal. It fixes the reliability problems of the 7.62x39 AK round in semiauto ARs cause by the Ak rounds extreme taper. It will use standard AR 5.56 magazines with no loss in capacity and will use all standard AR parts designed for the 5.56 except the barrel. Bolt and carrier will remain the same. The round has more energy out of a 9 inch barrel than the 5.56 does out of 16". Not only that, but it also sounds awesome...BLACKOUT! Hehe...that's what the enemy will do when they hear thats what you're bringing! Standard loads will include a 125, 155, and even a 220gr subsonic load pushing 500lbs muzzle energy. Now, as they say, I told you that story so I could tell you this story. I want in on this .300 BLk action. I want a 9" barrel and will throw a suppressor on it as well. But I don't want to pony up for the suppressor AND SBR paperwork at the same time cause I'm cheap. So I was thinking about building a pistol AR lower and throwing the 9" .300blk upper and suppressor on it for now, then filling for the SBR papers. But that got me thinking, I know owning a short barreled upper and a rifle lower can get you in trouble if you don't allready have the SBR papers.(what is it called? Intent to manufacture or something?) So, i allready own a 5.56 rifle. Once I have it and a .300blk pistol both in my possession, and since I can easily swap the uppers creating an SBR, would that count as intent to manufacture or whatever it's called? Or would I be safe from the BATFe boogeyman?