Is there an age restriction to transport a shotgun for trap shooting in Michigan?
Gun and ammo is properly cased.

After some more googling I found the answer.  I was wondering if a person under 18 could posses a shotgun in car while going to a trap event.  the answer is yes provided gun and ammo is secured properly.

http://www.legislature.mi.gov/%28S%28srpepcxniah1b12dp0yzny0d%29%29/mileg.aspx?page=getObject&objectName=mcl-750-234f