The following link outlines the requirements for non-commercial group uses on National Forest Lands. The only catch is when your player count goes over 75 then a non-commerical permit is required. Over 75 players then you have to get involved with the Forest Service and there are some provisions about "para-military training" that are pretty subjective and can be worked through with undertsanding by MOST local recreation staffs.
http://www.fs.fed.us/specialuses/specia ... p-noncom-aThis is all presuming that the AO is not in any area that is under a special closure order for firearms or any other special wildlife or fire order that would pose a problem. These are publicly available and are usually available at the front desk of a district office, as well as online.
There are no requirements for Bio BB's (although it's a nice jesture)