thank you for pointing out that a true pistol upper would need to go on a registered pistol lower. you could also legally be in posession of one if you have a registered SBR lower too without entering into that grey area of the law known as "constructive intent". Its definitely a legitimate concern for anyone dabbling in anything thats got a sub 16" barrel.
thankfully i got that covered with this 300 blk pistol, which will share the lower with the new upper
actually with a 13" barrel, in the most technical sense of the law, i wont have a pistol with that upper attached, i'll have a "firearm". pretty much a 13" version of the XO-26 firearm i mentioned in the last post. without going to a PDW style receiver extension and the complications that go with those style of receiver extensions, its damn near impossible to have an AR pistol with a barrel much longer than 9" - with a flash hider on it anyway - that being a firearm without a stock or VFG that's under 26" OAL and didnt start out its life as a rifle. I almost screwed the pooch on the above build and came in just a RCH shorter than the <26" OAL necessary with the build above in its original configuration (sig brace with a M.I. Sig buffer tube which is just a bit longer than a standard pistol buffer tube).
which is why i was exploring a 9" barrel option so that i could get under 26" with a ross brake and actually be able to treat it like a pistol under the MI CPL laws. no biggie to me, its easy enough to treat it otherwise, just like adding my suppressor turns the above pistol into a "firearm" too, so i cant carry it suppressed if i wanted to under the CPL law.
because unfortunately michigan doesnt measure at the shortest operable configuration possible (like without flash hider) like the BATFE does where non-permanent muzzle devices, etc dont count toward OAL.