| .55 Boys | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
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| Type | Anti-tank rifle cartridge | |||||||||||
| Place of origin | United Kingdom | |||||||||||
| Service history | ||||||||||||
| In service | 1937–1945 | |||||||||||
| Used by | United Kingdom Commonwealth of Nations Finland, et al. | |||||||||||
| Wars | World War II Winter War Continuation War | |||||||||||
| Production history | ||||||||||||
| Designed | 1937 | |||||||||||
| Manufacturer | Kynoch | |||||||||||
| Specifications | ||||||||||||
| Parent case | .50 BMG | |||||||||||
| Case type | Belted, bottleneck | |||||||||||
| Bullet diameter | 14.3 mm (.565 in) | |||||||||||
| Neck diameter | 15.392 mm (.606 in) | |||||||||||
| Shoulder diameter | 15.34 mm (.604 in) | |||||||||||
| Base diameter | 20.168 mm (.794 in) | |||||||||||
| Rim diameter | 20.244 mm (.797 in) | |||||||||||
| Rim thickness | 2.44 mm (.096 in) | |||||||||||
| Case length | 97.79 mm (3.85 in) | |||||||||||
| Overall length | 133.43 mm (5.253 in) | |||||||||||
| Ballistic performance | ||||||||||||
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| Test barrel length: 914.4 mm (36 in) Source(s): Ammo Encyclopedia, 2nd Edition by Michael Bussard | ||||||||||||
The .55 Boys (13.9×99mmB in metric) is an anti-tank cartridge used by the United Kingdom during World War II. It was designed for use with the Boys anti-tank rifle.