Searched but couldn't find anything definitive.

Can someone please break down the MI regulations re: AR pistols and how they mesh with Federal? If I understand this correctly, MI measures OAL from the shortest possible firing length (i.e. end of barrel sans muzzle device to end of buffer tube). If this OAL is less than 26 inches, it must be registered as a pistol regardless if it is built as a pistol or rifle/SBR. If the OAL is greater than 26 inches it's considered a firearm in Michigan but COULD be considered a pistol per Federal if it were built as such. Is this correct? I'm so confused on this

With the exception of an SBR, the issue is not how its built or marked. The issue is its definition.

28.421(c) "Firearm" means any weapon which will, is designed to, or may readily be converted to expel a projectile by action of an explosive.
28.421(i) "Pistol" means a loaded or unloaded firearm that is 26 inches or less in length, or a loaded or unloaded firearm that by its construction and appearance conceals it as a firearm.
MCL 750.222 (i) "Rifle" means a firearm designed or redesigned, made or remade, and intended to be fired from the shoulder and designed or redesigned and made or remade to use the energy of the explosive in a fixed metallic cartridge to fire only a single projectile through a rifled bore for each single pull of the trigger.
MCL 750.222  (k) "Short barreled rifle" means a rifle having 1 or more barrels less than 16 inches in length or a weapon made from a rifle, whether by alteration, modification, or otherwise, if the weapon as modified has an overall length of less than 26 inches.

Using AR’s as an example.
A pistol is one with no stock and OAL of 26 inches or less. Barrel length is irrelevant as long as its OAL is 26 inches or less. Pistols are registered under Michigan law.
A rifle is one with a stock and at least a barrel 16 inches in length and an OAL of more than 26 inches. Rifles of this class are not registered under Michigan law.
A SBR is one with a stock and barrel less than 16 inches OR one made from a rifle and an OAL of less than 26 inches.  Need a Form 1 first to make. Need to register under the Pistol registration statute if OAL is 26 inches or less.
A firearm is one with no stock with an OAL of more than 26 inches. Firearms of this class are not registered under Michigan law.
Dont overlook this build option.  For example, an AR lower with Sig Brace and 12 inch BBL and vertical front grip has an OAL of 27+ inches.  It is not a pistol, not a rifle, not an SBR and not an AOW.  
Its just a firearm. No registration or Form 1.
A sig brace is not a stock.
Add a vertical front grip to a handgun, however, and you have made an AOW.  Need a Form 1 first to make.

The federal definition of handgun and pistol are as follows:
“Handgun” is defined under Federal law to mean, in part, a firearm which has a short stock and
is designed to be held and fired by the use of a single hand…. 18 U.S.C. § 921(a)(29).
Under an implementing regulation of the National Firearms Act (NFA), 27 C.F.R. § 479.11,
“pistol” is defined as:
… a weapon originally designed, made, and intended to fire a projectile (bullet) from one or
more barrels when held in one hand, and having (a) a chamber(s) as an integral part(s) of, or
permanently aligned with, the bore(s); and (b) a short stock designed to be gripped by one hand
and at an angle to and extending below the line of the bore(s).

State law provides more definition of a pistol than federal and that is the one to comply with.

Others may freely comment if they differ about this.

See these links
MSP on SBRs
Adding vertical grip to a handgun is an AOW

Nailed it.

I like and took the Firearm route with 2 ARs.

@MichMan1

You mention sig brace.  I'm assuming that any brace will work with a 12" barrel to bring it to 27"+?  Is a P&W muzzle device counted in the OAL?  I know it is federally for rifles.  I have an 11.5" upper that I was planning a pistol build but I might P&W it if that gets me to the required length.

This is very helpful and exactly what I was hoping for. Thank you very much.

Not to revive anything too crazy however I also thought this would be a good thread to clarify my question vice start a new thread. My question pertains to how stripped lower receivers are registered in MI. If I purchase a stripped lower and then proceed to build an AR that qualifies as a "firearm" is this legal? Or are stripped lowers registered as rifles in which anything less than a 16" barrel would make it an SBR?

If I have a stripped lower, an SBA3 brace and a 12.5" barrel and I assembled this and put a vertical grip on it, would it legally be a firearm or SBR? I apologize if I am going in circles but I want to be sure that my next project won't make me a felon or get confiscated. My main concern is how a stripped lower is classified when purchased.

Thanks again

If it is a virgin stripped lower, it will be transferred as "Other" on a 4473. You may build it into whatever you would like.

In regards to your build, the brace means it cannot be a rifle. If the OAL is over 26", it is also not a pistol. As long as it's over 26", I believe you have a firearm. Under 26" and you're messing with an AOW by putting a vertical grip on a pistol. This is just my interpretation and IANAL.

Your exactly right

Don't count the muzzle brake in the OAL calculation.

The brace, bbl and receiver when assembled has to be over 26 inches to add the vertical forward grip and NOT be an AOW or SBR under federal law, and to BE a firearm (not a pistol which requires registration or rifle which does not) under state law.

So I think... or I am missing something but a scorpion evo micro with pistol brace is good to go?

Any permanently attached muzzle device would count for AOL though, correct?

What’s the barrel length and OAL?

Yes. My understanding is that MI would measure in the shortest configuration, including permanently attached components. Even things like AR stocks and braces which are relatively easy to remove are still considered permanent. Basically anything that’s not QD would be considered permanent.

So free float handguards that pass the crown on the barrel slightly, would that be considered in the measurement?  I'd think not if a brace isn't counted.  Since you don't need the hadguard to shoot the pistol.

PSA has this kit on sale, I'm worried that the 10.5" rail would put me slightly over the 26" length so I could have it loaded in my car.  In the pictures it looks like the end of the rail is slightly longer than the muzzle crown.

https://palmettostatearmory.com/psa-10-5-5-56-nato-1-7-nitride-10-5-lightweight-m-lok-classic-ept-sba3-pistol-kit-w-mbus-sight-set-gray.html

Kit has everything I'm looking for for my first pistol build, already have a virgin stripped lower that has been burning a whole in my pocket eerrr safe for a year lol

I could spend $10 more and get one with a 9" rail and no MBUS sights....