[Professional Engineer]

Ah, Thanks, or tanks!

[colorado tanker]

Tanks for the memories . . . .

[colorado tanker]

Here's an engineer's explanation for how the thing works.

The raised portion of tha barrel is a bore evacuator. As the round passes it, ports in the barrel pressurize the cylinder around the barrel. As the round exits the barrel, the pressure in the evacuator is released by angled ports that point toward the muzzle. The flowing gas from the evacuator pulls propellant gases away from the breach and keeps them from entering the turret.