In the game, the grenade launcher has a capacity of 1 grenade. However, the launcher is clearly based off of a design capable of holding six. I believe that increasing the capacity would also improve gameplay balance.

you can change that via overwriting the gun's data file ("data/cgm/guns/grenade_launcher.json")

{
   "general" : {
      ...
      "maxAmmo": 6,
      ...
   }
   ...
}

Thanks