That would be under the federal minimum requirement.
So how would an underfolder be long enough?

tag while i reference.
..............

Ok    

 NFA FAQ


" A short barreled rifle is a rifle (which is defined as a shoulder
fired, rifled bore firearm) with a barrel length of less than 16",
or an overall length of less than 26", or any weapon made from a
rifle falling into the same length parameters (like a pistol made
from a rifle).  In measuring barrel length you do it from the
closed breech to the muzzle, see 27 CFR sec. 179.11.  To measure
overall length do so along, "the distance between the extreme ends
of the weapon measured along a line parallel to the center line of
the bore." 27 CFR sec. 179.11.  On a folding stock weapon you
measure with the stock extended, provided the stock is not readily
detachable, and the weapon is meant to be fired from the shoulder."

Ah so its measured with the stock extended. Thanks.

Quoted: Ah so its measured with the stock extended. Thanks.

Thats the federal requirement, some states have their own laws that measure with the stock folded instead.  

Quoted: Quoted: Ah so its measured with the stock extended. Thanks. Thats the federal requirement, some states have their own laws that measure with the stock folded instead.

I think Michigan is one of those states.  You might have better luck in the Hometown forum.  I remember somebody made "long" US made slant brakes for states that had peculiar requirements.  Good luck to you.  UF are cool if you can get one.  

If it is less than 30", but longer than 26" it needs to be registered as a handgun in Michigan.

You need to add an AK74 type muzzle device or something to make it 26 in just to be meet the pistol portion of MI law. I think a slant break is something like 25.95 or something

What everyone else has said about MI :)  I live here as well.  DO NOT produce a rifle that is under 26" OAL with the stock FOLDED - the "opinion" (not law) of the ex AG has declared these to be illegal short barreled rifles.

Reference:

http://www.ag.state.mi.us/opinion/datafiles/1980s/op06280.htm

The good news:  contrary to bad local Police advice?  There is NOTHING in that opinion that references "fixed" muzzle devices, nor is the term "permanant" anywhere in the text.  So yes - thread your barrel if it isn't already threaded, and add a brake.  Get a really EVIL looking one :)