Colt XM16E1
- Category
- Assault Rifle
- Barrel
- 508 mm
- Weight, empty
- 3.18 kg
- Introduced
- 1964
About
What it is, and why it matters
The Colt XM16E1 was the U.S. Army trials and limited-issue model that bridged the original M16 (Model 601/602) and the standardized M16A1. Designated the Colt Model 603, it was the first member of the family to incorporate the forward assist plunger demanded by the Army so a soldier could manually close the bolt. The 'E' suffix marked its experimental/trials status; once type-classified as standard in 1967, the design was redesignated the M16A1.
The first forward-assist prototype was gold-plated and hand-polished, presented by Colt president Paul Benke to Army ordnance officer Howard Wheeler in 1964 to win over a service still uneasy about a rifle with no manual bolt-closure device.
Colt Model 603, produced from early 1964 until the early-1967 transition to the M16A1. Introduced the 'partial fence' reinforced lower receiver around the magazine release. The Air Force/Army dispute over the forward assist delayed standardization; the Army received the forward-assist XM16E1 while the Air Force kept the assist-less M16.
Specification
Everything measured
IdentityWhat it is, who built it and when.
- Manufacturer
- Colt's Manufacturing Company LLC
- Category
- Assault Rifle
- Country
- United States
- Status
- Out of production
- Produced
- 1964 to 1967
- Variant of
- Trials model
DimensionsAs issued, without a magazine or an optic.
- Barrel
- 508 mm
- Overall length
- 986 mm
- Sight radius
- 500 mm
- Weight, empty
- 3.18 kg
- Weight, loaded
- 3.90 kg
ActionHow it cycles, what trips it, and what feeds it.
- Action
- Gas operated direct impingement
- Firing mechanism
- Hammer fired
- Trigger
- Single stage
- Capacity
- 20
- Magazine
- Detachable box
MaterialsEach swatch is the material itself, not a colour chosen to stand for it.
- Frame
- Aluminum
- Barrel
- Steel
- Stock
- Polymer
- Finish
- Anodized
BallisticsFrom the service cartridge, not a handload.
- Muzzle velocity
- 975 m/s
- Muzzle energy
- 1693 J
- Effective range
- 400 m
- Maximum range
- 2653 m
- Rate of fire
- 750 rpm
Trajectory
What the round does downrange
Solved from the muzzle figures and the bullet. The dashed rule is the effective range on the record, and the crosses are the steps the solver returned.
Features
What it has
What the record lists as fitted, drawn from the catalogue.
Forward assist
Partial fence lower receiver
Fixed carry handle
Birdcage flash hider
Bayonet lug
Standing
How it compares
Each figure against the firearms of the same type and cartridge that record it, or of the same type where that cartridge has too few. Positions are read to the nearest tenth.
| Measurement | This firearm | Median | Position |
|---|---|---|---|
| Empty weightAmong 158 5.56x45mm NATO assault rifles | 3.18 kg | 3.60 kg | Lighter than about 80% |
| Overall lengthAmong 156 5.56x45mm NATO assault rifles | 986 mm | 920 mm | Longer than about 80% |
| Barrel lengthAmong 157 5.56x45mm NATO assault rifles | 508 mm | 449 mm | Longer than about 90% |
| Magazine capacityAmong 158 5.56x45mm NATO assault rifles | 20 | 30 | Among the smallest capacities |
Answers
Questions about the Colt XM16E1
How much does the Colt XM16E1 weigh?
The Colt XM16E1 weighs 3.18 kg (7.01 lb) empty and 3.90 kg (8.60 lb) loaded.
What caliber is the Colt XM16E1?
The Colt XM16E1 is chambered in 5.56x45mm NATO.
How many rounds does the Colt XM16E1 hold?
The Colt XM16E1 holds 20 rounds, fed from a detachable box magazine.
How long is the Colt XM16E1?
The Colt XM16E1 is 986 mm (38.8 in) long overall, with a 508 mm (20.0 in) barrel.
Who makes the Colt XM16E1?
The Colt XM16E1 is made by Colt's Manufacturing Company LLC (United States). It was designed by Eugene Stoner.
When was the Colt XM16E1 introduced?
The Colt XM16E1 was introduced in 1964 and discontinued in 1967.
How does the Colt XM16E1 operate?
The Colt XM16E1 uses a gas operated direct impingement action, and its firing mechanism is hammer fired.
Compatibility
Which parts fit this firearm
Studio
Every part that mounts on this, resolved
Not a list the maker typed out: the answer comes from the mounts this firearm exposes and the interface each part needs, so it stays right when either one changes.
- Every part that mounts on any firearm in the catalogue
- Interface standards, platforms and fit overrides
- The same answers through the API and the MCP server
Requires a signed-in GunSpec account on the Studio plan. The answer is computed per part, so it is not part of the public record.
Provenance
What the record holds
Every figure above was taken from one of these pages. The confidence reflects how much of the record came from a page a claim can be checked against.
In service
- United States Army
- 1964
- United States Marine Corps
- 1965
Provenance
Confidence in this record
72%
Stockists
Where to buy
Offers link straight to the shop. GunSpec never takes the order.
No shop has listed this firearm yet
Stock and prices come from the shops themselves. If you sell this firearm, you can list it and it appears here.
List a firearmMCP
Ask an assistant about it
The same record, reached the way a person asks for it rather than the way a program does.
Ask GunSpec
Works with
Point an MCP client at GunSpec and it answers from the catalogue rather than from memory. A free key covers the read tools.
API
The call that returns this record
The same fields, in the same units, from the same endpoint the page reads.
curl --request GET \ --url 'https://api.gunspec.io/v1/firearms/xm16e1' \ --header 'X-API-Key: your_key'{ "id": "xm16e1", "name": "Colt XM16E1", "manufacturer": { "id": "colt", "name": "Colt's Manufacturing Company LLC", "countryCode": "US", "foundedYear": 1855, "website": "https://www.colt.com", "logoUrl": null, "description": "American firearms manufacturer headquartered in Hartford, Connecticut. Founded in 1855 and now a subsidiary of Colt CZ Group, continuing production of iconic firearms including the 1911 pistol.", "status": "active", "defunctYear": null, "stateOwned": null, "makesFirearms": null, "parentId": null, "predecessorId": null, "createdAt": "2026-02-11 23:44:38", "updatedAt": "2026-02-18 03:43:38", "version": "7143c7ff3f7e156063a240f2df7b4746ee1c0394d7cd5f592d05bac43233d637" }, "category": { "id": "assault-rifle", "name": "Assault Rifle", "description": "Selective-fire rifles chambered in intermediate cartridges" }, "country_of_origin": "US", "year_introduced": 1964, "barrel_length_mm": 508, "weight_empty_g": 3180, "action_type": "gas_operated_direct_impingement"}