4 shotgun shells
From DoomWiki.org
The shotgun shells pickup provides four shells for the shotgun or super shotgun.
Doom's shotgun shells are magical. When a sergeant shoots at you, his shotgun fires four pellets. If you kill him and pick up his weapon, your shots will contain seven pellets. If you use the ammo for the super shotgun instead, you will fire twenty pellets in every double-barrelled blast.
