Allin Conversion
- Category
- Rifle
- Barrel
- 1020 mm
- Weight, empty
- 4.17 kg
- Introduced
- 1866
About
What it is, and why it matters
The Allin Conversion is a single-shot, breech-loading rifle developed at the U.S. Springfield Armory by Master Armorer Erskine S. Allin. Officially the Springfield Model 1866 (the Second Allin Conversion), it was created by milling out the breech of surplus Civil War muzzle-loading rifle-muskets and fitting a hinged 'trapdoor' breechblock, converting them to fire the metallic centerfire .50-70 Government cartridge. The design gave U.S. troops a rapid, reliable breechloader and established the trapdoor mechanism that would define American service rifles into the 1870s and 1880s.
Erskine S. Allin's conversion was prized as 'pure Yankee ingenuity', a cheap way to turn a mountain of obsolete Civil War muzzleloaders into modern breechloaders. At the 1867 Wagon Box Fight, soldiers armed with the new .50-70 trapdoors held off a far larger Sioux and Cheyenne force whose warriors expected the slow reload of muzzleloaders.
The 1866 'Second Allin Conversion' chambered the .50-70 Government cartridge, replacing the ineffective .58 rimfire of the earlier 1865 'First Allin Conversion'. It proved decisive at the Wagon Box Fight and Hayfield Fight (1867) along the Bozeman Trail.
Specification
Everything measured
IdentityWhat it is, who built it and when.
- Manufacturer
- Springfield Armory (US Government)
- Category
- Rifle
- Country
- United States
- Status
- Discontinued
- Produced
- 1866 to 1868
DimensionsAs issued, without a magazine or an optic.
- Barrel
- 1020 mm
- Overall length
- 1400 mm
- Weight, empty
- 4.17 kg
ActionHow it cycles, what trips it, and what feeds it.
- Action
- Trapdoor
- Firing mechanism
- Hammer fired
- Trigger
- Single action
- Capacity
- 1
MaterialsEach swatch is the material itself, not a colour chosen to stand for it.
- Frame
- Steel
- Barrel
- Steel
- Stock
- Walnut
- Finish
- Blued
BallisticsFrom the service cartridge, not a handload.
- Muzzle velocity
- 381 m/s
- Muzzle energy
- 2120 J
- Effective range
- 300 m
- Maximum range
- 900 m
- Rate of fire
- 10 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.
Hinged trapdoor breechblock- Converted muzzleloader
Open sights
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 1,612 rifles | 4.17 kg | 3.50 kg | Heavier than about 80% |
| Overall lengthAmong 1,557 rifles | 1400 mm | 1080 mm | Longer than about 90% |
| Barrel lengthAmong 1,659 rifles | 1020 mm | 584 mm | Longer than about 90% |
| Magazine capacityAmong 1,611 rifles | 1 | 5 | Holds fewer rounds than about 90% |
Answers
Questions about the Allin Conversion
How much does the Allin Conversion weigh?
The Allin Conversion weighs 4.17 kg (9.19 lb) empty.
What caliber is the Allin Conversion?
The Allin Conversion is chambered in .50-70 Government.
How many rounds does the Allin Conversion hold?
The Allin Conversion holds 1 rounds.
How long is the Allin Conversion?
The Allin Conversion is 1400 mm (55.1 in) long overall, with a 1020 mm (40.2 in) barrel.
Who makes the Allin Conversion?
The Allin Conversion is made by Springfield Armory (US Government) (United States). It was designed by Erskine S. Allin.
When was the Allin Conversion introduced?
The Allin Conversion was introduced in 1866 and discontinued in 1868.
How does the Allin Conversion operate?
The Allin Conversion uses a trapdoor 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
- 1866
- French Army
- 1870
Provenance
Confidence in this record
82%
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/allin-conversion' \ --header 'X-API-Key: your_key'{ "id": "allin-conversion", "name": "Allin Conversion", "manufacturer": { "id": "springfield-armory-us", "name": "Springfield Armory (US Government)", "countryCode": "US", "foundedYear": 1777, "website": "https://www.springfield-armory.com", "logoUrl": null, "description": null, "status": null, "defunctYear": null, "stateOwned": null, "makesFirearms": null, "parentId": null, "predecessorId": null, "createdAt": "2026-04-05 22:24:37", "updatedAt": "2026-04-05 22:24:37", "version": "b9dd0910a7c8bee7c58786e8b0a8f572a1d60da9a0b15c41d155cb38023c6bd8" }, "category": { "id": "rifle", "name": "Rifle", "description": "Long-barreled firearms designed for accurate shooting" }, "country_of_origin": "US", "year_introduced": 1866, "barrel_length_mm": 1020, "weight_empty_g": 4170, "action_type": "trapdoor"}