P90 Submachine Gun

By Dan Shea

The P90 was developed as a per- sonal weapon for support troops whose main function was not being a rifleman. US military veterans will remember the M3 “Greasegun” as a “Tanker’s gun”, that was found to be very useful to other troops. Many different elite groups used the “Greasegun” on a regular basis- it was accurate, easy to use, and very compact. In the same way, the P90 has crossed over from a sidearm for support troops to carry, into a tool of the tactical team and special operations personnel. The ballistics of the 5.7 x 28mm cartridge, combined with the high capacity of the magazine (50 rounds!), and the very comfortable compact design, have made the P90 a very attractive package. Not only is it compact, but the P90 is truly ambidextrous in its features. Ejection is straight down, and all operational devices are available to either the left or right hand.

Construction is of polymer materials except the operating parts (receiver, bolt, barrel), and they contribute to the light weight of the P90. Options include a built in laser target designator, and an accessory rail to allow flashlights or external lasers. Perhaps the most intriguing feature of the P90 lies not in the futuristic shape, nor in the new cartridge, but in the magazine itself. The P90 magazine is a somewhat standard double column stack magazine, but at the feed end, it has a channel that turns the cartridges ninety degrees for presentation in the line of the chamber. This allows the see-through magazine to lay flat along the top of the P90, contributing to the compactness of the design.

On firing the P90, it is the recoil itself that is so interesting, or rather the absence of anything significant. It is very similar to firing a .22 Long Rifle SMG. Recoil impulse comparisons with two other cartridges that many of the readers of SAR will be able to identify with firing should provide a common frame of reference so that you can understand what I mean by “Virtually no recoil”.

RECOIL IMPULSE COMPARISON

	9 x 19	5.7 x 28mm	5.56 NATO
Kgm/s	3.2	1.95	6.6
Lb.s	0.84	0.44	1.29

Live fire demos by FN personnel using tracer illustrate how controllable this system really is.

SAR noticed the P90 being carried by the special teams that effected the rescue of the hostages in the Japanese Embassy situation in Peru last year. Rumor from some personnel known to us has it that the P90 was extremely effective. This is the only combat/ operational use that we are aware of to date. Official word has not been put out on this.

5.7 x 28 mm AMMUNITION:

The key to FN’s newest offerings lies in the new ammunition. 5.7 x 28 mm is just as interesting and deserving of closer scrutiny as are the FiveseveN pistol and P90 submachine gun that utilize it. The roots of the new cartridge go back to the NATO request for a new cartridge to replace 9 x 19mm (Parabellum), to the 5.56mm and 6mm programs, the Small Caliber High Velocity (SCHV) program, and the backyard cartridge “Wildcatters” who have been experimenting for the last fifty or so years. The collected knowledge from all of the above, filtered through FN’s engineering department with their own new ideas, has yielded some impressive results.

The desire to have a new more effective weapon for support troops in the NATO block spawned several interesting cartridges. Most of the contenders utilized the research done in the 5.56mm (M16) development, looking for lower weight projectiles that could be driven to higher velocities and have more impressive terminal ballistics. The French corporation Giat had a 5.7 x 22 mm cartridge that was short lived, and FN produced the 5.7 x 28 mm utilized in these new designs.

5.7 x 28 mm projectiles, when fired from either the FiveseveN pistol or the P90 submachine gun, have very flat trajectories out to around 150 meters. If sighted in at 100 meters, the difference between trajectories at 10 meters and 100 meters is about 4 inches. They are still very accurate and effective out to 200 meters, easily maintaining an 8 inch group at that distance. Some very positive aspects of the cartridge are that it maintains its energy past 200 meters (Still equivalent to a 9mm round), will generally deliver all of its energy to a target, and starts rapidly losing energy after 400 meters. Contrast this with the 9mm Parabellum round that will easily kill or injure at over 800 meters, or the 5.56 mm NATO round that has deadly terminal ballistics out to a much further range.

The 31 grain projectile is somewhat controversial in effect, as are most new innovations that threaten the status quo. Gelatin block tests have proven the effectiveness of the cartridge’s terminal ballistics in theory, but to this point in time it is unproven on the battlefield. The armor piercing qualities of 5.7 x 28 mm are proven as well. Don’t expect to see this cartridge sold over the counter in the United States, in this incarnation it is strictly a law enforcement or military round. Several things that we do know about from testing make for a very positive future for it; first, the diameter of the case is about half that of the 9mm parabellum, allowing 50 rounds of ammunition in the same length magazine that would only allow 30 rounds of 9mm. Second, the weight of the 5.7 x 28 mm round is about half of either the 9mm or the 5.56 NATO round, allowing the operator to effectively carry almost twice the ammunition load.

Positive aspects of the recoil impulse of the new round are covered in the general text of this article, so the third truly remarkable feature of 5.7 x 28 mm is the behavior of the bullet in gelatin tests. All indications are that the new round will not deform or fragment- meeting standards from the Geneva Convention- but at about 2 inches of penetration it begins to tumble to 180 degrees. This produces a wound cavity that is similar to that of the 5.56 mm NATO ammunition used in the M16 series of rifles. The 5.7 x 28mm’s battlefield ability to penetrate modern ballistic armor and PASGT helmets is unquestioned. The effectiveness of the residual energy in the projectile after doing so has yet to be proven. Since 15 countries are now actively utilizing the new weapon systems, it should not be too long before the After Action reports come in.

TECHNICAL DATA 5.7 x 28 mm
Designation: SS190
Ammunition length: 1.6 inch
Ammunition weight: 93 grains
Projectile weight: 31 grains
Recoil impulse: 0.44 lb/s
Muzzle velocity: 2346 fps
Chamber pressure: 49,070 lb/in2
Types available: Ball (Copper jacket), Tracer (Red tip), Subsonic (White tip), Blank (Crimped green neck), Dummy (drilled case)

This article first appeared in Small Arms Review V1N11 (August 1998) and was posted online on March 3, 2017

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