So with all the information swamping the internet about SBR, I am overly confused and cannot find a direct answer in English from a reputable source.

I am in Michigan.

I understand that you can build an AR pistol using a lower that has never been registered as a rifle.
Then you have to register said lower as a pistol.

I can't find a straight answer on 80% lowers though. If you build a SBR/Pistol using an 80% lower, do you have to register it?

I searched these Michigan forums and found a lot on the SBR but cant find anything regarding building one with a 80% (no serial)

Yes, and you'll need a serial # too.

Same apply to an 80% 1911?

Yep

When the "lower" is in its 80% form, it is not a gun and is just a chunk of fancy metal.

When you finish machining it to 100%, it becomes an "other" firearm, which is neither a pistol nor rifle, and does not require registration.



The moment it does require registration is when you place a pistol/nfa upper on the lower, at which time it becomes a handgun/SBR and needs the respective paperwork.



For pistol registration you will need to add a serial number (whatever numbers you choose) and a manufacturer name on the gun so they can be recorded, the same info is required by the feds for an SBR build.

So once the upper/barrel is placed on which is in pistol/sbr spec, it would need to be registered. If that is the case, then I guess it would just be easier
to buy a completed lower with S/N on it already.

I just wish I could find the information in writing somewhere for Michigan so I can be 100% sure.