Chamber Gun is a gun. Its firing mode and appearance changes depending on which floor the player is on.
- Master's Chambers - Each Master Round the player carries permanently unlocks the mode of its respective floor. Reloading the Chamber Gun with a full magazine cycles through the unlocked modes.
- In the Keep of the Lead Lord, the Chamber Gun is a single target, semi-automatic gun.
- In the Oubliette, the Chamber Gun fires poison skulls.
- In the Gungeon Proper the Chamber Gun is a shotgun.
- In the Abbey of the True Gun the Chamber Gun is a piercing crossbow.
- In the Black Powder Mine, the Chamber Gun is a melee-range, high damage drill.
- In the Resourceful Rat's Lair, the Chamber Gun is a rocket launcher which fires cheese wheels that encheese enemies, similar to those fired by the Elimentaler.
- In the Hollow, the Chamber Gun is a combination of Glacier and The Exotic. It fires an ice cube projectile that bounces off walls and enemies, and leaves a trail of water. The projectile eventually bursts into several homing rockets.
- In the R&G Dept., the Chamber Gun is a pencil which functions similarly to the Wood Beam.
- In the Forge, the Chamber Gun is a beam weapon that shoots 2 homing beams of lava in a V-pattern.
- In Bullet Hell, the Chamber Gun is a homing chain beam similar to the Raiden Coil. It hits all visible enemies at once for high damage.
- All modes share the same ammo pool. Firing a shot in one mode reduces the ammo of the other modes by a proportional amount. For example, firing one shot in its Hollow mode uses up 10 shots of the base mode, because the base mode has 10 times the max ammo.
- At the start of each floor, the gun's ammo is fully replenished.
- If the player has Chance Bullets and does not switch to the Chamber Gun from a floor that does not have a Master Round (such as the Oubliette, Abbey of the True Gun, Resourceful Rat's Lair, or the R&G Dept.), other guns have a chance to shoot bullets from that firing mode.
- The synergy Master's Chambers does not work with Lich's Eye Bullets.
- For some players, firing the Chamber Gun in its Hollow mode causes a game crash.
- If the player has Ancient Hero's Bandana, after changing modes, ammo will not be quadrupled, but maximum ammo is still quadrupled.
- When in the R&G Dept., the gun may not switch to the pencil. Dropping the gun will change it to the pencil, but it will revert on reload.
- May be a function of which, if any, Master Rounds are present (Tested with 2, 3 & 4).
- If the Chamber Gun is taken into any floor where it cannot usually be taken (for example, the various character's pasts) using game modification, reloading the gun on a full clip will cause the game to crash as it has no valid form to switch to.
- If the gun has been Duct Taped to another, the combo may be lost upon arriving in the R&G Dept.
Chamber Gun in the Keep of the Lead Lord.
Chamber Gun in the Oubliette.
Chamber Gun in the Gungeon Proper.
Chamber Gun in the Abbey of the True Gun.
Chamber Gun in the Black Powder Mine.
Chamber Gun in the Resourceful Rat's Lair.
Chamber Gun in the Hollow.
Chamber Gun in the R&G Dept.
Chamber Gun in the Forge.
Chamber Gun in Bullet Hell.