A Holy Man once said it isn't what you put in the body, but how it comes out. These go in small and come out ....
Well, let's see. We're talking about Border patrol guys taking fire, so it's either a single guy or a pair, with enough of the bandito shooters that they can fire and maneuver around them/him. They're in close enough they figure can do the job with small arms, yet were far enough away that with handguns or pistol-caliber buzzguns, they didn't hit or injure any of their BP targets...this time. So what's needed is a small, concealable and powerful weapon that can let one guy ruin the cover and movement of six or eight attackers, yet carry enough ammo with the weapon to get the job done. That likely lets out 40-pound, five-foot long M82 .50 caliber Barretts, though a Barrett 25mm *payload rifle* might be a possibility, though still heavy and not especially maneuverable. And at least a 500-meter range is needed, with a minimal *shoot at me here* muzzle flash, and enough edge to get a hit even with a near miss....
So we have to go to the past and out of the US inventory for an ideal answer....Surprise, surprise....
