imported post
OK, I've got a question that will probably result in a call to the ATF to be 100% sure, but I'll post it up here in case some one y'all have any personal experience with a similar situation...
I have an extra complete Bushmaster AR-15 in a M4 configuration, as I bought it in a while back. I'm working on a fixed-stock 24" barrel one to replace it as my .223 target rifle, so, I've been trying to decide what to do with the M4 I have lying around. I've been thinking about turning it into a pistol, stick on a pistol buffer in place of the stock and getting a new pic-rail upper with a 10.5" barrel. And to start off with, I live in Colorado, so no worries about "assault pistol" bans or other ridiculous stuff along that line.
My concern comes up with the ATF's policy on machineguns; that even the trigger or stock from a M-16 is a "machinegun," since "once a machinegun, always a machinegun." Since the lower receiver has the serial number and was originally configured as a rifle, I'm wondering if it's "rifle-ness" would remain despite my reconfiguring it. A 10.5" barrel, no stock, and one pistol grip puts it squarely in the Title 1 category of non-restricted pistol, but I don't want to run afoul of creating a SBR in case the "rifle-ness" wins out.
So, anyone have any experience with this? I'd hate to buy a new lower just for a original-pistol-configuration serial number...