[KarmaInferno]

That second picture looks more like the standoff tip for a door breaching shotgun system.




-k

[savaze]

I've only ever seen a door breaching shotgun in pictures.  Though I have seen an M203 used to unhinge doors with the jumbo buckshot rounds.

[Outsider]

Question. Is the gas vent supposed to be a flash suppressor/ muzzle break? Or is it something totally different?

[Rockopolis]

It's a muzzle brake, or some more advanced variant thereof.  Can't use it with any kind of suppressor, actually.

[savaze]

Question. Is the gas vent supposed to be a flash suppressor/ muzzle break? Or is it something totally different?

Muzzle breaks/gas vents are actually the opposite of a flash suppressor.  Everyone around you knows when you fired as well because it works by venting the gases to help counteract recoil, that whole Newton's 3rd Law dealio. 

gas vent = bigger flash + more debris moved