The BSA still has a "Marksmanship" merit badge. When I was a scout (got my Eagle in 1982), it was all about long guns--rifles and shotguns. We could bring our own .22 rifles to summer camp, but there were NO pistols allowed, and NO firearms at other camps. And at summer camp, you had to check it in at the armory on the range and leave it there.
I visited the 2010 National Jamboree at Ft. A.P. Hill last summer, and the rifle range used high-powered .22 air rifles. But Remington had a trap and skeet range with 20ga 870s.
From what I know, no firearms are allowed at Scouting events--even for leaders or ScoutMasters under official BSA National rules--even if yo have a carry permit.
It is a stupid policy--I agree. Scout leaders have to be over 21, and must pass background checks these days. There is NO reason a Scoutmaster shouldn't be allowed to carry--OC or CC--if he is not a prohibited person.
I am a proud Eagle Scout, but there are things about Scouting (on the National administration level) that I'm not very proud of--and this is one of them...