http://www.nraila.org/statelawpdfs/MTSL.pdf
this site is really fun to browse
http://www.gunbroker.com/
and i'm sure if you're nice, and have some badass guns, as well as believe in the America that our forefathers did you'd fit in with these folks.
http://www.militiaofmontana.com/
this guy had the right idea.

but yea, you can own everything short of a bazooka in Montana. Mostly because Montana hosts the largest militia in the US of A.
where do i apply!!?
"The strongest reason for the people to retain the
right to keep and bear arms is, as a last resort,
to protect against tyranny in government."
-Thomas Jefferson