Image credit
- Title
- File:FN P90 PDW.jpg
- Author
- DickClarkMises
- Licence
- CC0 — public domain dedication
- Source
- https://commons.wikimedia.org/wiki/File:FN_P90_PDW.jpg
How Muzzle energy is calculated
E = ½ · m · v²
Not calculated: v has no sourced figure yet. Nothing is substituted for a missing input.
1 of 2 inputs link to their source.
How Muzzle velocity is calculated
no sourced velocity for this load
Not calculated: muzzle velocity has no sourced figure yet. Nothing is substituted for a missing input.
No input on this calculation carries a clickable source yet.
How Loaded mass is calculated
m_loaded = m_empty + m_magazine + n · m_cartridge
Not calculated: m_magazine has no sourced figure yet. Nothing is substituted for a missing input.
Assumptions
- One magazine, filled to the stated capacity. Spare magazines, optics, slings and lights are the owner’s, not the arm’s.
2 of 4 inputs link to their source.
How Free recoil is calculated
E_recoil = ½ · m_firearm · v_recoil²
Not calculated: v_recoil has no sourced figure yet. Nothing is substituted for a missing input.
Assumptions
- Propellant gas momentum is excluded: ARMAG does not record charge weights (SPEC.md §14). This is therefore a lower bound on the real free recoil, consistent between entries but smaller than a figure that includes the gas term.
- Free recoil: the arm is unrestrained. Stock design, muzzle devices, stance and shooter mass are not modelled, because none of them is a property of the arm.
1 of 2 inputs link to their source.
How Capacity is calculated
as published for the primary chambering
Inputs
- capacity50verifiedsourceDetachable box magazine lying flat along the top of the receiver.
1 of 1 inputs link to their source.
Derived figures
Computed from the sourced values above. Open ƒ on any figure for the formula, its inputs, and the assumptions it makes.
How Momentum is calculated
p = m · v
Not calculated: v has no sourced figure yet. Nothing is substituted for a missing input.
1 of 2 inputs link to their source.
How Sectional density is calculated
SD = mass(gr) / (7000 · diameter(in)²)
Inputs
- mass2.009 g31.00 grverifiedsourcePublished as 31 gr; 1 gr = 0.06479891 g exactly.
- diameter5.7 mm0.2244 inverifiedsourceC.I.P. G1, maximum bullet diameter.
Assumptions
- Reported in the conventional lb/in² so it is directly comparable with published figures.
2 of 2 inputs link to their source.
How Power factor is calculated
PF = mass(gr) · velocity(fps) / 1000
Not calculated: velocity has no sourced figure yet. Nothing is substituted for a missing input.
Assumptions
- A competition classification defined by the IPSC and USPSA rulebooks, stated in their units. It describes a scoring category, not an effect.
1 of 2 inputs link to their source.
How Magazine dump is calculated
t = (n − 1) / (rpm / 60)
Inputs
- n50verifiedsourceDetachable box magazine lying flat along the top of the receiver.
- rpm975 rpmestimatedsourceThe article publishes 850–1,100 rounds/min. Recorded as the midpoint of that range.
Assumptions
- Cyclic rate held for the whole magazine, no stoppages, trigger held down. A theoretical figure for comparing mechanisms, not a measured one.
2 of 2 inputs link to their source.
How Sight error at 1 mm is calculated
θ = atan(misalignment / sight radius)
Not calculated: sight radius has no sourced figure yet. Nothing is substituted for a missing input.
Assumptions
- Shows what a stated aiming error costs. The misalignment is the reader’s figure; the site does not claim how well anyone aims.
No input on this calculation carries a clickable source yet.
Specifications
Every row here is generated from the schema, so a figure recorded on this entry cannot be missing from the table — and the same rows, read the same way, are what the comparison shows.
Identity
- Action
- Self-loading
- Fire modes
- Semi-automatic
- Fully automatic
- Operating system
- Blowback, simple
- Designed in
- Belgium
- Produced in
- Introduced
- 1990
- Production
- 1990–present
Dimensions and mass
- Mass, empty
- 2.631 kg5.800 lbsource
Published as 5.8 lb; 1 lb = 0.45359237 kg exactly. P90; the PS90 is published at 6.28 lb.
- Magazine, empty
- not recorded
- Length
- 505 mm19.88 insource
P90; the PS90 is 666 mm.
- Length, folded
- not recorded
- Width
- 55 mm2.165 insource
- Height
- 210 mm8.268 insource
- Barrel length
- 264 mm10.39 insource
P90; the PS90 barrel is 407 mm.
Sights and rifling
- Sight radius
- not recorded
- Sight height over bore
- not recorded
- Rifling twist
- not recorded
- Twist direction
- not recorded
- Grooves
- not recorded
- Sight graduation
- not recorded
Chamberings
- FN 5.7×28mmprimary50 rounds
Scale
A to-scale outline against family siblings. The dimensions are sourced; the shape is a representative outline for the type, and says so.
- FN P90505 mm19.88 in
Representative outline — the dimensions are sourced, the shape is not. Overall length, and barrel length where recorded, are drawn from this entry's own figures; the profile is a generic one for the firearm type and says nothing about this arm's actual contours.
Detail
The magazine is the design. Fifty rounds lie flat along the top of the weapon, parallel to the barrel, and a spiral ramp at the front rotates each cartridge ninety degrees as it feeds. That is why a weapon 505 mm long carries fifty rounds without a magazine protruding anywhere, and why the P90 is shaped like nothing that came before it.
Everything else follows from wanting that magazine and a bullpup layout together. Spent cases eject downwards through the pistol grip, so the weapon is genuinely ambidextrous — the only one on this site of which that is straightforwardly true. The 5.7×28mm cartridge is mild enough that a simple blowback breech will hold it, so there is no gas system at all.
It was FN’s entry against the same 1989 NATO personal-defence requirement that produced Heckler & Koch’s MP7, and neither cartridge became a standard. Adoption has been steady rather than wide: special-purpose units, some police forces, and the Secret Service.
The cited article publishes its cyclic rate as a 250 rpm range, so that figure here is an estimate.
References
This entry's own bibliography. Every citation key on this page resolves into this list.
- FN P90 · Wikipedia · 1368378586 · read 2026-08-31 · CC BY-SA 4.0
Last verified 2026-08-31 · review status: agent-populated