Clip

Ammo clips are an ammo pickup containing 10 bullets for the pistol or chaingun (20 at the I'm Too Young To Die and Nightmare! skill levels). The clips dropped by slain zombie troopers and SS Nazis contain only 5 bullets (10 at the I'm Too Young To Die and Nightmare! skill levels) and, unlike preexisting clips, disappear when crushed beneath doors or moving ceilings.

Each bullet does between 5 and 15 hit points of damage (determined using Doom's pseudorandom number generator). Note that, although shots fired by troopers and SS Nazis inflict only 3-15 points each, the bullets in their dropped ammo clips behave like any other bullets when used by the player.

Although referred to in the game as clips, the objects depicted are clearly magazines; that is to say, they contain bullets rather than merely hold them in place. Then again, in real life, magazines, especially pistol magazines, are sometimes refered to as "clips". 

Appearance statistics
The IWADs contain the following numbers of ammo clips (excluding those of dead Troopers):