Anyone know if we can legally own a M203 here in MIchigan?

Negetive. No DD.

Hell,all allowed Class III stuff has to be C&R as well as cans.

37mm is ok
40mm is a no-no
whether or not the 37mm is an M203, i don't really know.

www.37mm.com

Destructive Devices are legal in michigan, as are Any Other Weapons.  If you look through the laws you will see no law banning their possesion, therefore it is legal.

Dont take our word for it, dont take the web's word either. Call the PD and ask, or go there and ask to read the law's. They will help.

"They guys at ar15.com said it is ok!" wont work...

I asked ATF if they would approve an AOW transfer of a supershorty as an AOW.  But would have to be registered as a pistol?  There is sort of a reverse logic here. If your local PD chief signs off on the Transfer and you pay the $5 and then go back to the PD to get a green card as a pistol, will the PD say No?  Probably not.
Thus while the feds are OK with an AOW, will the state be OK with it?  The ATF suggested that the Mich AG give an opinion to that effect.  I can post the letter if someone tells me how.

Does anyone actually own an AOW here?  I'd like to get an uzi AOW.