Hmm.............. so.............. the infamous ammo glitch and the "double damage" exploit.

Been witnessing a 13 min gold solo this morning: 


He's using the double damage glitch, enabled by using two types of ammo at once.

How to enable the glitch:
- Pick an ammo type on your left booster.
- Pick another ammo type on your right booster.
Your character screen appears as if you only have 1 type of ammo equipped. However, check the "Inspect Squad" menu: both ammo are equipped on your character.

No big deal so far, but the game thinks that each ammo type equals one bullet, so each time you shot, one bullet for the Ammo type 1 (ex: Cryo in left booster) will be shot and one bullet for the Ammo type 2 (ex: Incendiary in right booster) will be shot, resulting in double damage. 

In-game, the ammo type icons overlaps. Both ammo are used during the game. You can also do that with other types of consummables (XP for instance)

Happy grinding.