For policy and justification, you may want to get in touch with Peter Tarly here:
I went to one of their operator's courses when I did the carbine policy and training proposal for my department.
I work in Vermont and he made it clear that should the need arise he would be available for follow on contact despite the fact that he lives and works in New York.
He definitely knows the ins and outs of the policy and verbage required to make a successful pitch to your higher ups.
Based on his information and other, much smaller pieces from numerous sources, I got my proposal approved with no issues.
AR-15 or varients or Mini 14 .223/ 5.56. Ammo approved and provided by department, as well as the standard liability crap. PM me and I'll email you my final draft of the policy if you want.