M40A3
- Category
- Sniper Rifle
- Barrel
- 610 mm
- Weight, empty
- 7.50 kg
- Introduced
- 2001
About
What it is, and why it matters
The M40A3 is the third generation of the USMC's M40 sniper rifle series, developed from 1996 to 2001 and placed into service during Operation Enduring Freedom. Built on the Remington Model 700 short-action receiver, the M40A3 represented a significant modernization over the M40A1, featuring a McMillan A4 fiberglass stock with adjustable cheekpiece and spacers for customized length of pull, a 24-inch Schneider match-grade heavy stainless steel barrel, and a Picatinny rail for optics mounting. The rifle retained the proven 5-round internal box magazine and bolt-action operation that defined the M40 series. Like all M40 variants, each rifle was individually hand-built by USMC armorers at the Precision Weapons Section, Marine Corps Base Quantico, maintaining the tradition of custom-built sniper rifles that began with the original M40 in 1966.
The M40A3 saw its combat baptism during the opening stages of Operation Enduring Freedom in Afghanistan in 2001, and went on to serve through some of the most intense urban and desert combat of the Iraq War. USMC Scout Snipers armed with M40A3 rifles played a critical role during the Second Battle of Fallujah in 2004, where sniper teams provided overwatch during house-to-house clearing operations. The transition from the Unertl 10x fixed scope to the Schmidt & Bender variable-power scope gave Marine snipers significantly more versatility in close-quarters and long-range engagements.
Development of the M40A3 began in 1996 under the direction of the Marine Corps Scout Sniper School and the Precision Weapons Section at Quantico. The primary improvements over the M40A1 were the McMillan A4 stock with adjustable cheekpiece (replacing the A1 stock), the Schneider match-grade barrel (replacing the Atkinson/Hart barrel), and the addition of a Picatinny rail (replacing the Unertl-specific scope mount). The standard optic was the Schmidt & Bender 3-12x50 PM II LP scope, replacing the Unertl 10x fixed-power scope that had served since the M40A1. The M40A3 served through the heaviest fighting in Iraq and Afghanistan before being replaced by the M40A5 beginning in 2009.
Specification
Everything measured
IdentityWhat it is, who built it and when.
- Manufacturer
- Remington Arms
- Category
- Sniper Rifle
- Country
- United States
- Status
- Out of production
- Produced
- 2001 to 2009
- Variant of
- Predecessor
DimensionsAs issued, without a magazine or an optic.
- Barrel
- 610 mm
- Overall length
- 1124 mm
- Weight, empty
- 7.50 kg
- Weight, loaded
- 8.20 kg
ActionHow it cycles, what trips it, and what feeds it.
- Action
- Bolt action
- Firing mechanism
- Striker fired
- Trigger
- Single stage
- Trigger pull
- 27.0 N
- Capacity
- 5
- Magazine
- Fixed box
MaterialsEach swatch is the material itself, not a colour chosen to stand for it.
- Frame
- Steel
- Barrel
- Stainless steel
- Stock
- Fiberglass composite
- Finish
- Matte black
BallisticsFrom the service cartridge, not a handload.
- Muzzle velocity
- 777 m/s
- Muzzle energy
- 2867 J
- Effective range
- 915 m
- Maximum range
- 3725 m
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.
Free floating barrel
Heavy barrel
Aluminum bedding block
Adjustable cheek piece
Adjustable length of pull
Picatinny rail
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 80 7.62x51mm NATO sniper rifles | 7.50 kg | 5.04 kg | Among the heaviest tenth |
| Overall lengthAmong 80 7.62x51mm NATO sniper rifles | 1124 mm | 1116 mm | Longer than about 60% |
| Barrel lengthAmong 80 7.62x51mm NATO sniper rifles | 610 mm | 559 mm | Longer than about 70% |
| Magazine capacityAmong 80 7.62x51mm NATO sniper rifles | 5 | 15 | Holds fewer rounds than about 80% |
Answers
Questions about the M40A3
How much does the M40A3 weigh?
The M40A3 weighs 7.50 kg (16.53 lb) empty and 8.20 kg (18.08 lb) loaded.
What caliber is the M40A3?
The M40A3 is chambered in 7.62x51mm NATO.
How many rounds does the M40A3 hold?
The M40A3 holds 5 rounds, fed from a fixed box magazine.
How long is the M40A3?
The M40A3 is 1124 mm (44.3 in) long overall, with a 610 mm (24.0 in) barrel.
Who makes the M40A3?
The M40A3 is made by Remington Arms (United States).
When was the M40A3 introduced?
The M40A3 was introduced in 2001 and discontinued in 2009.
How does the M40A3 operate?
The M40A3 uses a bolt action, and its firing mechanism is striker 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 Marine Corps
- 2001
Provenance
Confidence in this record
84%
Stockists
Where to buy
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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/m40a3' \ --header 'X-API-Key: your_key'{ "id": "m40a3", "name": "M40A3", "manufacturer": { "id": "remington", "name": "Remington Arms", "countryCode": "US", "foundedYear": 1816, "website": "https://www.remarms.com", "logoUrl": null, "description": null, "status": "active", "defunctYear": null, "stateOwned": null, "makesFirearms": null, "parentId": null, "predecessorId": null, "createdAt": "2026-02-11 23:44:38", "updatedAt": "2026-02-18 03:40:45", "version": "f839df62af811e3e261014e3302be8a7e112b5d78fb2f9f7bfad68d74817c9c8" }, "category": { "id": "sniper-rifle", "name": "Sniper Rifle", "description": "Precision rifles optimized for long-range accuracy" }, "country_of_origin": "US", "year_introduced": 2001, "barrel_length_mm": 610, "weight_empty_g": 7500, "action_type": "bolt_action"}