Image credit
- Title
- File:SMG XM177 COMMANDO 1.jpg
- Author
- Springfield Armory National Historic Site
- Licence
- Public domain
- Source
- https://commons.wikimedia.org/wiki/File:SMG_XM177_COMMANDO_1.jpg
How Muzzle energy is calculated
E = ½ · m · v²
Inputs
- m4.018 g62.01 grverifiedsource62 gr as published, converted to grams.
- v905.3 m/s2,970 fpsverifiedMeasured with a 368.3 mm barrel, not this arm's 254 mm. Velocity outside the sourced range is not projected.
1 of 2 inputs link to their source.
How Muzzle velocity is calculated
nearest sourced barrel length, no extrapolation
Inputs
- v at 368.3 mm905.3 m/s2,970 fpsverifiedsourceTable 2-1, muzzle velocity for the M4: 2,970 fps.
Assumptions
- This figure belongs to a 368.3 mm barrel. It is shown because it is the closest measurement that exists, not because it applies here.
1 of 1 inputs link to their source.
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.
3 of 4 inputs link to their source.
How Free recoil is calculated
E_recoil = ½ · m_firearm · v_recoil²
Inputs
- m_firearm2.43 kg5.357 lbestimatedsourceConverted from 5.35 lb, from the infobox; no inline citation is given there.
- v_recoil1.497 m/s4.911 fpsestimated
Assumptions
- Propellant gas momentum is excluded: ARMAG does not record charge weights. 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
- capacity30estimatedsource30-round box magazine or other STANAG magazines, from the infobox, uncited there.
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
Inputs
- m4.018 g62.01 grverifiedsource62 gr as published, converted to grams.
- v905.3 m/s2,970 fpsverifiedMeasured with a 368.3 mm barrel, not this arm's 254 mm. Velocity outside the sourced range is not projected.
1 of 2 inputs link to their source.
How Sectional density is calculated
SD = mass(gr) / (7000 · diameter(in)²)
Inputs
- mass4.018 g62.01 grverifiedsource62 gr as published, converted to grams.
- diameter5.7 mm0.2244 inestimatedsourceNo free NATO dimensional standard is published. The C.I.P. datasheet for the .223 Remington, which shares this bullet, gives a cartridge-maximum bullet diameter of 5.70 mm.
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
Inputs
- mass4.018 g62.01 grverifiedsource62 gr as published, converted to grams.
- velocity905.3 m/s2,970 fpsverifiedMeasured with a 368.3 mm barrel, not this arm's 254 mm. Velocity outside the sourced range is not projected.
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)
Not calculated: rpm has no sourced figure yet. Nothing is substituted for a missing input.
Assumptions
- Cyclic rate held for the whole magazine, no stoppages, trigger held down. A theoretical figure for comparing mechanisms, not a measured one.
1 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.
Variants
XM177E2
A slightly longer-barrelled version of the XM177E1 adopted for wider US Army special-operations use in Vietnam, adding a permanently attached moderator that lengthened the weapon overall.
- Length
stock extended, from the infobox, uncited there.
- Length, folded
stock retracted, from the infobox, uncited there.
- Barrel length
from the infobox, uncited there.
GAU-5/A
The US Air Force's designation for the XM177E1, issued to aircrew and security forces rather than through Army channels but mechanically identical.
GAU-5A/A
The US Air Force's designation for the XM177E2.
- Length
stock extended, from the infobox, uncited there.
- Length, folded
stock retracted, from the infobox, uncited there.
- Barrel length
from the infobox, uncited there.
| Variant | Years | Changes |
|---|---|---|
| XM177E2 | — | Length, Length, folded, Barrel length |
| GAU-5/A | — | no spec change |
| GAU-5A/A | — | Length, Length, folded, Barrel length |
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
- Type
- Carbine
- Action
- Self-loading
- Fire modes
- Semi-automatic
- Fully automatic
- Operating system
- Gas, direct impingement
- Roles
- Designed in
- United States
- Produced in
- Introduced
- 1966
- Production
- not recorded
Dimensions and mass
- Mass, empty
Converted from 5.35 lb, from the infobox; no inline citation is given there.
- Magazine, empty
- not recorded
- Length
XM177E1, stock extended, from the infobox, uncited there.
- Length, folded
XM177E1, stock retracted, from the infobox, uncited there.
- Width
- not recorded
- Height
- not recorded
- Barrel length
XM177E1, from the infobox, uncited there.
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
Operation
- Cyclic rate
- not recorded
- Trigger pull
- not recorded
- Effective range
from the infobox, uncited there.
- Units produced
- not recorded
- Launch price
- not recorded
Chamberings
- 5.56x45mm NATOprimary30 rounds
- .223 Remington30 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.
- CAR-15 XM177 Commando787.4 mm31.00 inheight not recorded
- Colt M4 Carbine838.2 mm33.00 inheight not recorded
- La France M16K673.1 mm26.50 inheight not recorded
- M16 rifle1,007 mm39.63 inheight not recorded
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. CAR-15 XM177 Commando, Colt M4 Carbine, La France M16K, M16 rifle record no height, so their outline is drawn at the type's proportion. That height is part of the shape, not a measurement.
Lineage
This design
- Derived from M16 rifle
Family
Gallery
Image credit
- Title
- File:SEAL Colt Commando v2.jpg
- Author
- JO1 (SS) PETER D. SUNDBERG
- Licence
- Public domain
- Source
- https://commons.wikimedia.org/wiki/File:SEAL_Colt_Commando_v2.jpg
Detail
“CAR-15” named an entire family of shortened M16 derivatives Colt offered in the mid-1960s, but only one member of that family generated real interest from the military: the Commando carbine, fielded by the US Army and Air Force as the XM177. It answered a need the standard M16 could not: a rifle short enough to use inside an armoured vehicle, a boat or a helicopter without a soldier fighting the length of the barrel and stock in a confined space.
Cutting the barrel down to roughly a third of the M16’s length created a new problem the short receiver alone could not solve, so Colt fitted a distinctive cylindrical moderator ahead of the front sight. Its job was not to silence the weapon: the cited article describes it primarily as a counterweight against a balance the shortened barrel had upset, which incidentally also reduced the sharp muzzle flash and made the report closer to a full-length M16A1’s than to an unsuppressed short carbine’s.
Deployment stayed narrow. The Army bought 2,815 XM177E1s in 1966, issued mainly to Navy SEALs and Army Special Forces, and later added 510 of the slightly longer XM177E2 for MACV-SOG operations in Vietnam; the Air Force adopted its own near-identical GAU-5/A and GAU-5A/A for aircrew and security forces. The four variants recorded here differ only in barrel length, overall length and the presence of the longer moderator, so they share this entry’s action, operating system and cartridge rather than standing as separate entries.
Every figure in this entry traces to the Wikipedia infobox without an inline citation and is recorded as
estimated. The wider CAR-15 line’s other proposed submachine-gun and automatic-rifle variants are not
modelled here. No twist rate is published, and no free dimensional standard exists for 5.56×45mm NATO
independent of its commercial equivalent.
References
This entry's own bibliography. Every citation key on this page resolves into this list.
- CAR-15 · Wikipedia · 1368013368 · read 2026-09-09 · CC BY-SA 4.0
Last verified 2026-09-09 · review status: agent-populated