SHOOT TO LOOT - Shooting any type of ammo picks it up.
In Destiny, SHOOT TO LOOT is a Weapon Upgrade that can be found on uncommon and rare Scout Rifles and uncommon Sniper Rifles in the game. Weapons in Destiny pull each Upgrade at random from specific pools (with a few Weapons that are an exception).
To see more info on exactly which Weapons this Upgrade can be found upon click the link below:
To see more about how this Weapon Upgrade fits into these pools, please click the links below:
SCOUT RIFLE WEAPON UPGRADES
SNIPER RIFLE WEAPON UPGRADES