Plasma Rifle

The plasma gun is Doom’s rapid-fire projectile weapon, firing blue plasma bolts at a rate of 700 shots per minute. It uses energy cells and combines high sustained damage with fast projectile velocity. Its position in the game’s automatic weapon-switch system also gives it a distinct role when the player’s current weapon runs out of ammunition. The plasma gun is one of the weapons covered in our Doom weapons database which provides a broader reference to the series’ arsenal.

Design and appearance

Visually, the weapon is built around a segmented barrel and a distinctive silhouette that id Software derived from a real-world prop: a dart-shooting, M60-like toy gun that was popular in the early 1990s. The designers detached a section of that toy and reversed it, giving the plasma gun its unusual, backward-facing front end. The resemblance to the original toy is most visible at the end of a firing volley, when the player’s hand lifts the weapon. In the Doom press release beta, the gun produced alternating green-white and orange-red plasma bursts; for the commercial release those were standardized to the familiar blue-and-white projectiles.

Where it first appears

Players encounter the plasma gun for the first time in a secret area of E2M1: Deimos Anomaly, the opening map of The Shores of Hell episode. From that point it appears in every level of the episode except the Tower of Babel. The first non-secret placement is in E2M5: Command Center. In Doom II, the earliest standard appearance is MAP05: The Waste Tunnels, though in multiplayer the weapon is available as early as MAP01: Entryway.

Ammunition and pickup values

The plasma gun draws on the same pool of energy cells shared with the BFG9000. Picking up the weapon itself grants 40 units of energy — 80 on the “I’m Too Young to Die” and “Nightmare!” skill levels. The player’s maximum cell capacity is 300, doubling to 600 after collecting a backpack. The weapon occupies slot 6 on the weapon carousel.

An energy cell provides 20 units of ammunition, while an energy cell pack provides 100. Both amounts are doubled on “I’m Too Young to Die” and “Nightmare!” The backpack doubles the maximum (300 to 600) and separately gives you 20 cells of ammo.

Combat characteristics

Each plasma burst inflicts between 5 and 40 points of damage. In continuous fire, the gun releases one burst every 3 tics — approximately 0.086 seconds — for a theoretical rate of 700.0 shots per minute. Releasing the trigger introduces a 20-tic pause (about 0.6 seconds) before the weapon is ready to fire again. Projectiles move at 25 map units per tic, equivalent to 875 map units every second. The Doom Wiki notes that the plasma gun’s damage rate is approximately three times that of the chaingun, making it far more efficient in terms of damage delivered per second.

Because the damage roll per shot varies so widely, the number of shots required to eliminate any given enemy spans a range rather than a fixed count. Against the lighter infantry, the figures are low: a zombieman typically needs 1 shot, while a shotgun guy about 2 shots. Mid-tier enemies require more sustained fire — a revenant takes roughly 14 shots, a cacodemon around 18, and a mancubus typically 27. The heaviest targets demand the most: the cyberdemon’s mean elimination count sits at approximately 179 shots, while the spiderdemon is at about 134 shots.

A tactical quirk worth noting is the weapon’s interaction with horizontal auto-aim. In close quarters, the engine’s auto-aim can redirect plasma bursts into nearby walls when the nearest monster is not squarely in front of the player. The Doom Wiki cites E4M2: Perfect Hatred as a concrete example: attacking the cyberdemon there without entering its line of sight requires deliberately aiming slightly to the monster’s left to compensate. Additionally, the rapid stream of projectiles tends to push lighter airborne enemies backward and sideways, scattering them out of the stream — a behavior that rewards controlled bursts over full-automatic fire against flying targets.

One practical side effect of the low damage threshold on weak enemies is that the plasma gun can gib zombiemen and shotgun guys, owing to their low hit-point totals of 20 and 30 respectively.

Priority in the auto-switch system

Doom’s source code (specifically P_CheckAmmo in P_PSPR.C) reveals that the plasma gun is checked first in the automatic weapon-switching order. The automatic weapon-switching order when a weapon runs dry reads: plasma gun > super shotgun > chaingun > shotgun > pistol > chainsaw > rocket launcher > BFG9000 > fist. A direct consequence of this ordering is that running out of BFG ammo (which requires 40 cells per shot) while the player still holds enough cells for plasma shots will cause an automatic switch to the plasma gun rather than a lower-tier weapon.

The Doom 64 variant

In Doom 64, the plasma gun received entirely redrawn sprites. A blue electric tube runs along the top of the weapon and emits a constant buzzing sound. The recoil animation was removed, likely to conserve cartridge space. The fire rate slows to one projectile every 4 tics; because Doom 64 runs at 30 tics per second rather than 35, this translates to one shot every 0.133 seconds and a rate of 450.0 shots per minute. Projectile velocity increases to 40 map units per tic (1,200 map units per second). Releasing the trigger no longer imposes any cooldown pause — the weapon resets instantly with no delay before the next shot.

Rapid-fire and performance considerations

The plasma gun’s sustained rate of fire means that many plasma-ball sprites must be rendered and tracked simultaneously during prolonged volleys. This has been known to cause lag during multiplayer games or on older machines.

In the modern games

The plasma gun and plasma rifle returned in different forms across later id Software games. In Doom 3, the plasma gun can be found in a hidden location in Alpha Labs Sector 3; it uses its own plasma-cell ammunition, has visibly slower projectiles than the classic weapon, and displays ammunition on a counter built into the weapon. In Doom (2016), the Plasma Rifle uses Argent-enhanced energy ammunition and has a Heat Blast weapon mod; its primary fire deals 25 direct damage plus 10 splash damage within a 96-unit radius. In Doom Eternal, the Plasma Rifle is obtained in Exultia and can overload energy shields when it depletes them.

Relatives in other id Software games

The plasma gun also has counterparts elsewhere in id Software’s games. Quake II features the HyperBlaster, while Quake III Arena features a plasma gun that can deal splash damage.