Bullets in this world seem to be plot devices that only work when they want the plot to advance. The rest of the time they turn into storm trooper projectiles. Also that trigger discipline yo, or rather total lack thereof. Additionally, I somehow feel hunting with a grenade launcher or even automatic weapons seems counter intuitive to the actual act of hunting. Even if you win, you have done so much damage to the carcass, you are decreasing your own income while increasing expenses in spent ammo.
Based around power shot, he should have gone with a semi auto high caliber weapon imo. Shotgun or anti material rifle. Then again with bullet behavior in this world, who knows.