Here is the GTA V Grenade Launcher from GTA V.

V2 - decals fixed

If you want to follow my weapon converting program, you must add it to the game with the Ryosuke's Weapon Limit Adjuster (http://hotmist.ddo.jp/plugin/wlimit/wlimit04.zip)
After that, follow the istruction in the readme for installing it.
[ALL MISTERIX 4 WEAPON RELEASED IN THE PAST NEEDED]

Credits:
ZAZ, for make the script "grenade launcher.cs" (i've edited it with rifle animation)
Ryosuke, for his Weapon Limit Adjuster
Automan, the creator of Misterix, for his help with some stuffs
arthuros mazonakis, for decals