Welcome to the UAC Matthew 8966 (Security Chief)
The Union Aerospace Corporation ( UAC ) is a fictional company|fictional conglomerate (company)conglomerate focused on military-industrial complex|military-industrial research in id Software|id Software's science fiction video game series Doom series|Doom. The corporation is depicted to be involved in advanced weapons development, biological research space exploration and teleportation. Set in the 22nd century|22nd century, the UAC is shown to have access to research facilities on other planets and moons within the Solar System such as Mars, Phobos (moon)|Phobos and Io (moon)|Io. In the video games, the UAC's research into teleportation unwittingly allows for the forces of Hell to invade from their realm and attempt to take over humanity.
The Uac has the most advanced technology ever made The Series 3 plasma gun in Doom 3 is slightly different from its earlier counterpart. It is now "clip" fed, fires at a slightly slower rate, but is simply one of the handiest weapons to have around.
The Plasma Gun can sustain a high rate of fire, can hold plenty of rounds in a cell but the projectiles move slower than the classic equivalent, however it is now extremely effective for taking out explosive projectiles launched at the player due to its high rate of fire and projectile size. It still deals good damage and is good for taking out mid-air rockets. Not in Xbox Deathmatch. Ammo counter is located on the weapon.  Tactical Use
A plasma gun is a trusty weapon indeed, and many have seen fit to call it the "projectile killer". The actual plasma shots themselves are very large and fire with an accuracy better than that of the chaingun (approximately 0.1 degrees of spread), making them ideal for taking out projectiles fired by other monsters. This means that if ample ammo is available to you, Imps, Revenants and even Mancubi are no longer a hassle.
Take into consideration that this stratagem is NOT effective against the Cyberdemon's rockets and that it is easier to simply outrun them.
The plasma gun also has a decent damage per shot ratio and a very good rate of fire. The only limitations would be the speed of the actual projectiles and the limit of the fifty round "clips".
Employing the plasma gun should be done in short to medium quarters, albeit the accuracy of the weapon makes it relatively effective at long range as well, provided that the enemy is not moving much. All low range monsters make easy target practice for the plasma gun, albeit ammo should be conserved for higher end monsters such as the Revenant and Mancubus. The slow speed of the projectiles means that flying monsters such as Cacodemons can be very difficult to hit unless at very short range; the faster chaingun is recommended against them.  Notes
The plasma gun no longer uses the same ammunition as the BFG 9000.
The plasma gun has a similar design to the Thompson submachine gun.
The first bit of ammo for the Plasma Gun you can find is in the Mars City Underground, hidden in a utility locker along with a Health Dispenser.