This hasn't been brought up, but, using non-standard weapons, in a combat zone, can be fatal. Quick story.
OCS graduate came to Nam with a 44. Magnum. In combat, he pulled and fired his 44. The different sound of the 44 attracted VC attention, that proved fatal.
I've often wondered if the same has occured in our current conflicts, and, if that, in itself, doesn't make some of these questions moot? I can understand if the weapon is chambered in a common caliber, like .223, 308, 9mm, or, a long range weapon, where the location will not be so easy to assess.
Perhaps a modified Thompson, to shoot 9mm?
Also, does different cylcing rates attract attention?
Why lug a Thompson, when a Cobray Mac10 weighs half the weight, is one of the easiest guns in the world to dissasemble and clean, and, with ball ammo, are incredibly reliable, not to mention near water proof?
S