Lindcott Armory Rifle · Military standard
.55 Boys
Anti-tank rifle cartridge developed for the Boys Mk I anti-tank rifle.
- Caliber
- 0.565″ · 14.351 mm
- Introduced
- 1937
- Case
- Rimless
- Primary use
- Military, Anti-Materiel
- Status
- Discontinued
- Introduced
- 1937
- Type
- Rifle
- Origin
- United Kingdom
- Inventor
- Boys Antitank Rifle design team
- Manufacturer
- Kynoch
- Standard
- Military standard
- Status
- Discontinued
- Availability
- Collector
- Case capacity
- 210 gr H₂O
- Twist (typical)
- 1:15
- Primer
- Berdan Large Rifle
- Case type
- Rimless
- Max pressure
- 68,000 psi
- Eff. range
- 300 yd
- Max range
- 800 yd
- Recoil
- 70–90 ft·lb
Ballistics
- Parent case
- —
Representative trajectory — modeled from a single velocity input (no published BC for this cartridge yet).
Performance
Buy links open .55 Boys ammunition at Rivertown Munitions.
Dimensionscase measurements · scale drawing · size vs familiar rounds
Case dimensions — the scale drawing at the top of the page is built from these.
Wikipedia · approximate| Measure | mm | in | ✓ |
|---|---|---|---|
| Bullet ⌀ | 14.35 | 0.565 | · |
| Neck ⌀ | 15.39 | 0.606 | · |
| Shoulder ⌀ | 15.34 | 0.604 | ~ |
| Shoulder angle | — | — | |
| Base ⌀ | 20.17 | 0.794 | · |
| Rim ⌀ | 20.24 | 0.797 | · |
| Belt ⌀ | n/a | ||
| Rim thickness | 2.44 | 0.096 | ~ |
| Neck length | — | — | |
| Case length | 97.79 | 3.850 | · |
| Overall length | 133.43 | 5.253 | · |
Size vs familiar rounds
Drawn at true 1:1 — every case is accurate relative to the others. Absolute size depends on your screen's pixel density, so measuring one against a real ruler may be off. .55 Boys is highlighted below.
Missing a dimension for .55 Boys? Some case measurements aren't in a published SAAMI/CIP drawing yet. Have a factory or reamer print? Send it → — verified hard-to-find data earns a free Lindcott sticker.
Factory loads
In production — 7 active loads across 7 brands. Top 15 shown · see all 20 →.
| Brand | Load | Grain | Bullet | FPS | ft·lb | BC |
|---|---|---|---|---|---|---|
| DAG | Standard | 930 | AP | 2,900 | 17,364 | — |
| Nammo | Standard | 930 | FMJ | 2,900 | 17,364 | — |
| RWS | Standard | 930 | FMJ | 2,900 | 17,364 | — |
| PPU | Range | 930 | FMJ | 2,900 | 17,364 | — |
| Wolf | Range | 930 | FMJ | 2,900 | 17,364 | — |
| Kynoch | Standard | 930 | FMJ-API | 2,900 | 17,364 | — |
| Buffalo Arms | FMJ Reproduction | 926 | FMJ | 2,800 | 16,117 | — |
| Royal Laboratory Woolwich | Ball FMJ | 926 | FMJ | 2,800 | 16,117 | — |
| Eley | AP FMJ Service | 926 | AP FMJ | 2,800 | 16,117 | — |
| Kynoch | AP FMJ Service | 926 | AP FMJ | 2,800 | 16,117 | — |
| Doubletap | Hardcast | 926 | FMJ | 2,750 | 15,547 | — |
| Jamison | Custom | 926 | FMJ | 2,750 | 15,547 | — |
| HSM Ammunition | Cowboy | 926 | FMJ | 2,750 | 15,547 | — |
| Hirtenberger | Standard | 926 | FMJ | 2,750 | 15,547 | — |
| OWS | Standard | 926 | FMJ | 2,750 | 15,547 | — |
Velocities are manufacturer-stated (test-barrel). Discontinued loads dimmed.
Reloading costestimate cost per round vs factory
Estimate your cost per round and how it compares to factory. Inputs are yours — nothing is stored.
Cost estimate only — not load data. Charge weight is your input; follow published manuals for safe charges.
Firearms chambered in .55 Boys
2 models in the database chamber .55 Boys. Browse all →
Connected reference
History
Developed in 1937 for the Boys Antitank Rifle, which entered service with the British Army in 1939. Effective against early German and Italian light armor, the Boys became obsolete as tank armor thickened. It saw extended use against softer targets, APCs, and light vehicles in North Africa and the Pacific. The Canadian Army used the Boys effectively in the Pacific Theater against Japanese light vehicles. Ammunition production ended post-WWII; cases are rare and expensive.
FAQs
- What twist rate does .55 Boys use?
- .55 Boys typically uses a 1:15 twist rate.
- What bullet diameter is .55 Boys?
- .55 Boys uses a 0.565″ (14.351 mm) diameter bullet.
- Is .55 Boys still in production?
- .55 Boys is discontinued; typical availability is collector.
- What is .55 Boys used for?
- .55 Boys is primarily used for military, anti-materiel.
Sources & provenance
Data & sources. Specs compiled from the Lindcott Armory reference; availability counted from 7 live factory loads; the trajectory is modeled (point-mass), not measured. See methodology. Spotted an error? Report it →