Springfield SPIW
- Category
- Assault Rifle
- Barrel
- 660 mm
- Weight, empty
- 5.00 kg
- Introduced
- 1963
About
What it is, and why it matters
The Springfield SPIW is an experimental American assault rifle developed by Springfield Armory for the U.S. Army's Special Purpose Individual Weapon program of the 1960s. It fired the 5.6x44mm XM144 flechette cartridge from a 60-round magazine at a cyclic rate of up to 1,700 rounds per minute, and carried an integral three-shot 40mm grenade launcher beneath the barrel. Built first as a bullpup and later in a conventional layout, the design never entered service: like the rival AAI, Winchester and Harrington & Richardson submissions, it was too heavy and unreliable, and the program was abandoned in favor of the M16.
The SPIW program sought a futuristic infantry weapon firing fin-stabilized flechette darts at extreme velocity, but every contender, including Springfield's, busted the 10-pound weight limit and the flechette ammunition proved finicky, leaving the conventional M16 to soldier on.
The 1964 bullpup prototype, with its distinctive 60-round staggered box magazine loaded behind the pistol grip, is the best-known Springfield SPIW and is preserved at the U.S. Army Ordnance Museum. Later 1965-1966 revisions moved to a conventional layout, adopted the Winchester-style grenade launcher, and used the improved XM216 flechette round.
Specification
Everything measured
IdentityWhat it is, who built it and when.
- Manufacturer
- Springfield Armory, Inc.
- Category
- Assault Rifle
- Country
- United States
- Status
- Prototype
- Produced
- 1963 to 1966
DimensionsAs issued, without a magazine or an optic.
- Barrel
- 660 mm
- Overall length
- 965 mm
- Weight, empty
- 5.00 kg
- Weight, loaded
- 6.40 kg
ActionHow it cycles, what trips it, and what feeds it.
- Action
- Gas operated
- Firing mechanism
- Hammer fired
- Capacity
- 60
- Magazine
- Detachable box
MaterialsEach swatch is the material itself, not a colour chosen to stand for it.
- Frame
- Steel
- Barrel
- Steel
- Finish
- Parkerized
BallisticsFrom the service cartridge, not a handload.
- Muzzle velocity
- 1402 m/s
- Muzzle energy
- 648 J
- Effective range
- 500 m
- Rate of fire
- 1700 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.
No load solved for this record yetThe flight path is computed from a cartridge and a bullet. This record has no ammunition filed against its chambering, so there is nothing to solve.
Features
What it has
What the record lists as fitted, drawn from the catalogue.
Integral grenade launcher
Flechette ammunition- High cyclic rate burst
60 round magazine
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 274 assault rifles | 5.00 kg | 3.58 kg | Heavier than about 90% |
| Overall lengthAmong 271 assault rifles | 965 mm | 915 mm | Longer than about 80% |
| Barrel lengthAmong 271 assault rifles | 660 mm | 415 mm | Among the longest tenth |
| Magazine capacityAmong 276 assault rifles | 60 | 30 | Among the largest capacities |
Answers
Questions about the Springfield SPIW
How much does the Springfield SPIW weigh?
The Springfield SPIW weighs 5.00 kg (11.02 lb) empty and 6.40 kg (14.11 lb) loaded.
What caliber is the Springfield SPIW?
The Springfield SPIW is chambered in 5.6mm Flechette.
How many rounds does the Springfield SPIW hold?
The Springfield SPIW holds 60 rounds, fed from a detachable box magazine.
How long is the Springfield SPIW?
The Springfield SPIW is 965 mm (38.0 in) long overall, with a 660 mm (26.0 in) barrel.
Who makes the Springfield SPIW?
The Springfield SPIW is made by Springfield Armory, Inc. (United States). It was designed by Springfield Armory.
When was the Springfield SPIW introduced?
The Springfield SPIW was introduced in 1963 and discontinued in 1966.
How does the Springfield SPIW operate?
The Springfield SPIW uses a gas operated 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
- United States
Provenance
Confidence in this record
70%
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/springfield-spiw' \ --header 'X-API-Key: your_key'{ "id": "springfield-spiw", "name": "Springfield SPIW", "manufacturer": { "id": "springfield-armory", "name": "Springfield Armory, Inc.", "countryCode": "US", "foundedYear": 1974, "website": "https://www.springfield-armory.com", "logoUrl": null, "description": null, "status": null, "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": "25f76dc992edbd0bbf9fcae464532e0cdea93a1bb7636f2858e213931d45a359" }, "category": { "id": "assault-rifle", "name": "Assault Rifle", "description": "Selective-fire rifles chambered in intermediate cartridges" }, "country_of_origin": "US", "year_introduced": 1963, "barrel_length_mm": 660, "weight_empty_g": 5000, "action_type": "gas_operated"}