The FN P90 Personal Defense Weapon is the standard submachine gun for SG-1 since the mission to P3X-888, as well as the standard issue weapon for the Atlantis expedition. (SG1: "The First Ones", SGA: "Rising")
It was selected as a standard issue weapon because it offered better armor-penetrating and killing power than the 9mm H&K MP5A3 submachine gun it replaced. Like other firearms, it is technologically primitive compared to Goa'uld, Wraith, and Ori weapons, but it is more than capable of piercing the armor worn by Jaffa, Ori soldiers, and Wraith warriors. According to Colonel Jack O'Neill, it is a weapon of war, designed to kill the enemy, and holds better offensive capabilities than the Staff weapon, which he said was designed primarily to intimidate. This is very true; the projectile weapons of the Tau'ri are among the most lethal encountered. Considered "primitive" mainly because they are not energy based, weapons like the P90, M16, and G36K are superior in combat against staff weapons due to their rapid firing rate and precision. They can easily penetrate the armor of a Jaffa, killing them. Even the M1911A1 and M9 Beretta pistols can keep a smaller group of Jaffa at bay for some time, and even kill them even when they are wearing armor. (SG1: "The Warrior")
Stargate Command uses the standard P90, distinguished by the angular-cut sight. Contrary to popular belief, the P90 does not have an integral red-dot sight (an aspect that was present on the Tokyo Marui P90), but rather a day/night sight that offers two different reticles; the first was circular and colored white, while the second, the night-time sight, was an "open-T" design which glowed red via use of tritium. Depending on light conditions, the sight would automatically adjust or fade between the two graticules, granting the user a reliable aiming reference at all times. This is the original variant as issued in the SGC.
In reality, the day-time 'white-sight' was eventually made black as the original design had a tendency to wash-out against sunlight during the daytime. The sight changes were suggested by the US Secret Service, who issues it as a part of their standard arsenal. The sight module was/is manufactured by Ring Sights and is noticeably rectangular, with a blue lens-face.
Other features of the SGC P90 are two mounting rails on either side of the upper receiver. Using these rails, accessories (such as a Kull disruptor, laser sight, Naquadah powered lasers, or flashlights which are commonly shown on nearly every weapon can be attached and utilized as a part of the weapon itself.
Although the P90 has been standard SGC issue since 2000, Dr. Daniel Jackson and Teal'c have only begun using the weapon in recent years. Up until that point Teal'c used his staff weapon and Dr. Jackson utilized Berettas. (SG1: "Avalon, Part 1", "The Quest, Part 1")
When the Odyssey was overcome by Replicators, Colonel Samantha Carter and Major Kevin Marks used P90s to keep the Replicators bay and to stop them from gaining access to the Asgard computer core. (SG1: "The Ark of Truth")
- The P90 is classified as a Personal Defense Weapon (PDW). It is a class of weapon designed for close-range self-defense by support troops, gunners, and vehicle crews or use in Close Quarter Battle by commandos and anti-terrorist/hostage rescue teams.
- Major Samantha Carter erroneously describes the P90's rounds as being "teflon-coated" when they are actually copper-jacketed. Though this may have been a reference to the brass which is coated in a polymer that could indeed contain Teflon in order to help it feed reliably in the p90s unique magazine (SG1: "The Warrior")
- One of the reasons the "Carter Special" was created was to address a shortage of P90 blanks during Season 7. According to an interview with Amanda Tapping, this was due to the increased demand for P90 ammo during the invasion of Iraq.