Just my opinion, it's meant as constructive criticism, please don't take it personal: Interesting idea, but the clip a bit bulky and the recoil would be quite heavy without any sort of muzzle break. Besides that, designing a grenade launcher with a fully automatic firing mode would make no sense with a weapon with such a small clip if it can't be box- or belt-fed also. Granted, the Milkor MGL is semi-automatic and fully automatic.
Hm, and i wouldn't call a clip-using grenade launcher "automatic" if its rate of fire is 10 round per minute(!), as the notes state, that's only 1 round in 6 seconds. I can't imagine how to achieve such a slow reloading cycle with an (gas-operated?) autoloader. But YMMV.
Regarding the rest: Superb artwork, proportions are ok.
p.s.: Just minor nuisances, but it's "grenade" and "Terran" (If you did mean "from Earth", if you did mean by "Terrain" that it's hill and mountains and stuff, then the spelling is correct.)