No use hiding this anymore. If you set grenade launcher in one slot and a gun in the other, then u can do the rapid fire grenader glitch. Do this by switching from the grenade launcher to the gun and then switchonf back quickly. Might be tricky thr first tries but it gets really easy. Works for slim grenader and lava.

This happens to the that ammo depletion glitch ur talking about. Somehow transfers the lost ammo into grenade launcher ammo and gives u rapid fire. Thid glitch has been out since the lsuncher was released and ive reported this countless time. Its still not fixed so i guess its meant to be!