The FN P90 is one of the most recognizable submachine guns in modern firearms, largely due to its distinctive bullpup design and the unique curved magazine that feeds from the top. Understanding how a P90 clip works requires looking at the weapon’s specific feeding mechanism, which is engineered to reliably cycle the proprietary 5.7x28mm ammunition without relying on traditional box magazines. This system is designed to function optimally under high rates of fire and demanding conditions, making it a critical component of the platform’s legendary 950 rounds per minute cyclic rate.
The Fundamentals of the P90 Magazine
At the heart of the feeding system is the P90 magazine, which is often mistakenly called a "clip" by observers. Technically, the P90 uses a true magazine that is inserted into the top of the receiver via a distinctive hinge. This magazine is transparent, allowing the shooter to visually track remaining rounds, and it houses the ammunition in a spiral configuration. This design is not merely aesthetic; it is a functional necessity that allows the 50-round capacity to fit within the compact frame of the weapon while maintaining proper cartridge alignment for the feeding process.
The Twin-Pronged Feeding Mechanism
Inside the magazine well, the P90 employs a sophisticated twin-pawl follower system to manage the ammunition. As the bolt cycles rearward to eject a spent casing, it simultaneously strips a round from the magazine. The follower uses two small metal flanges, or "paws," that engage the rim of the cartridge. These paws are specifically designed to lift the round from the spiral track, elevate it to the correct height, and then guide it into the chamber. This dual-pawl arrangement ensures positive feeding, preventing failures to feed even when the weapon is subjected to extreme recoil or rapid successive shots.
How the Cartridge Travels to the Chamber
Once the round is stripped from the magazine, it does not simply fall down into the chamber due to gravity. The P90 features a proprietary curved feed ramp located above the magazine well. This ramp acts as a track, catching the cartridge as it is ejected by the follower and redirecting it 180 degrees. The geometry of this ramp is critical, as it gently guides the round into the chamber without causing it to tumble, which could result in a malfunction. The entire process is so efficient that the weapon can transition from the last round in the magazine to a round ready to fire in a fraction of a second.
Addressing the "Clip" Misconception
It is important to clarify the terminology surrounding the P90 supply system. While enthusiasts and media often refer to the device as a "clip," this is technically inaccurate. A clip is a device that holds cartridges together for insertion into a magazine, such as a stripper clip used with an AR-15 or an en-bloc clip used in an M1 Garand. The P90 magazine is a self-contained, disposable or reloadable box that holds the ammunition under spring pressure and feeds it directly into the weapon. Referring to it as a magazine is correct and helps distinguish the P90’s advanced feeding system from older, simpler technologies.
The Role of the Magazine Spring
Driving the entire feeding operation is a heavy-duty spring housed within the magazine body. This spring is responsible for pushing the follower—and consequently the stack of ammunition—upward toward the feed ramp. The tension of this spring is calibrated to match the specific dimensions and weight of the 5.7x28mm round. As rounds are fired, the spring contracts to provide consistent upward pressure, ensuring that the next round is always in the optimal position for the twin paws to grab. This constant pressure is what allows the P90 to maintain a high rate of fire without the shooter needing to manipulate the action manually.
