.55-inch

Calibre specification
Metric (mm) Imperial (in)
Calibre 13.9 x 99 .55
Name: Boys
Case Type: Belted, bottlenecked
Bullet Diameter: 14.30
Case Length: 99.1
Rim Diameter: 20.26
Neck Diameter: 15.39
Shoulder Diameter:
Base Diameter: 20.27
Total Length: 133.9
Weight: 125 grammes
Primer: Berdan
Year Introduced: 1937
Also known as:
  • .55 Boys W Mk I or W Mk II
  • 13.9mm Patrone
  • 14×99
Countries using this calibre
United Kingdom (Experimental)

Sources: