Colt M4 Carbine
Colt's Manufacturing Company1987–presentPost-Cold War
Also known as M4, Carbine, Caliber 5.56 mm, M4, R0977
Image credit
- Title
- PEO M4 Carbine RAS M68 CCO
- Author
- Photo Courtesy of PEO Soldier
- Licence
- Public domain
- Source
- https://commons.wikimedia.org/wiki/File:PEO_M4_Carbine_RAS_M68_CCO.png
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 fpsverified
1 of 2 inputs link to their source.
How Muzzle velocity is calculated
measured at this barrel length
Inputs
- v905.3 m/s2,970 fpsverifiedsourceTable 2-1, muzzle velocity for the M4: 2,970 fps.
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_firearm2.944 kg6.490 lbverifiedsourceTable 2-1, weight without magazine and sling, 6.49 lb.
- v_recoil1.236 m/s4.054 fpsestimated
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
- capacity30verifiedsourceSTANAG 4179 magazine.
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 fpsverified
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 fpsverified
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.
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.
Variants
M4A1
Fully automatic in place of the three-round burst, and from 2014 a heavier barrel profile and an ambidextrous selector.
M4 MWS
Modular Weapon System: the handguard is replaced by a rail adapter carrying MIL-STD-1913 rails on all four faces.
| Variant | Years | Changes |
|---|---|---|
| M4A1 | — | Fire modes |
| M4 MWS | — | no spec change |
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
- Burst
- Operating system
- Gas, direct impingement
- Designed in
- United States
- Produced in
- Introduced
- 1994
- Production
- 1987–present
Dimensions and mass
- Mass, empty
- 2.944 kg6.490 lbsource
Table 2-1, weight without magazine and sling, 6.49 lb.
- Magazine, empty
- not recorded
- Length
- 838.2 mm33.00 insource
Buttstock open.
- Length, folded
- 755.6 mm29.75 insource
Buttstock closed. The stock telescopes rather than folding, over four positions.
- Width
- not recorded
- Height
- not recorded
- Barrel length
- 368.3 mm14.50 insource
14.5 in, from the maker's catalogue.
Sights and rifling
- Sight radius
- not recorded
- Sight height over bore
- not recorded
- Rifling twist
- 177.8 mm7.000 insource
Table 2-1, right hand, one turn in 7 in.
- Twist direction
- Right
- Grooves
- not recorded
- Sight graduation
- not recorded
Operation
- Cyclic rate
- not recordedsource
FM 3-22.9 Table 2-1 gives 700 to 900 rounds per minute for the M4. TM 9-1005-319-10 gives 700 to 970 for the same weapon. Two Army publications disagree about the upper bound, so no figure is recorded.
- Trigger pull
- not recorded
- Effective range
- 500 m546.8 ydsource
Maximum effective range against point targets. Against area targets the manual gives 600 m.
- Units produced
- not recorded
- Launch price
- not recorded
Chamberings
- 5.56x45mm NATOprimary30 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.
- 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
- Smith & Wesson M&P15 Sport III889 mm35.00 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. 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
- Colt M4 MWS Carbine Iraq
- Author
- Staff Sergeant James Harper Jr., United States Air Force
- Licence
- Public domain
- Source
- https://commons.wikimedia.org/wiki/File:Colt_M4_MWS_Carbine_Iraq.jpg
Image credit
- Title
- M4A1-flattop
- Author
- Source: PEO SoldierDerivative: User:MathKnight
- Licence
- Public domain
- Source
- https://commons.wikimedia.org/wiki/File:M4A1-flattop.png
Detail
The M4 is an M16A2 with five and a half inches taken out of the barrel and a stock that telescopes, which sounds like a small change and is not. Shortening the barrel moved the gas port closer to the chamber, so the port pressure is higher and the bolt unlocks earlier and harder, and every subsequent argument about carbine reliability, buffer weights and gas port diameters descends from that geometry. The United States Army adopted it in 1994 and it displaced the full-length rifle almost completely within a decade.
Its designation is the one that made the promotion rule necessary on this site. The M4 is an AR-15 platform arm and could have been a variant tab on that page; it is a separate entry because it carries its own adopted military designation and its own dimensions, and the platform page owns neither. The M4A1, by contrast, differs in fire control and barrel profile and is a tab here rather than a page.
The cyclic rate is the interesting failure. Two United States Army publications describing the same carbine give different upper bounds, 900 rounds per minute in the marksmanship manual and 970 in the operator’s manual, so this page shows no cyclic rate at all and says why. Choosing one of them would have been the easy thing and would have been an invention.
References
This entry's own bibliography. Every citation key on this page resolves into this list.
- FM 3-22.9, Rifle Marksmanship M16A1, M16A2/3, M16A4 and M4 Carbine · Headquarters, Department of the Army · 2003 · FM 3-22.9 (FM 23-9), Change 1 · read 2026-08-27 · public domain
- TM 9-1005-319-10, Operator's Manual, Rifle 5.56 mm M16A2/M16A3/M16A4 and Carbine M4/M4A1 · Headquarters, Department of the Army · 2010 · TM 9-1005-319-10, Revision 2 (2010) · read 2026-08-27 · public domain
- Colt Military and Law Enforcement Catalog, Q2 2026 · Colt's Manufacturing Company · 2026 · read 2026-08-27
- M4 carbine · 1371259998 · read 2026-08-27 · CC BY-SA 4.0
Last verified 2026-08-27 · review status: spot-checked