British standard ordnance weights and measurements

The British standard ordnance weights and measurements for the artillery were established by the Master General of Ordnance in 1764, and these were not altered until 1919 when the metric system was additionally introduced.

This system has largely been replaced by a calibre system, which is the standard today for most weapon systems in use by the world's armed forces.

The 18th century standards were based on projectile weight, and dated back to use of muzzle loaded cannons which fired solid cannonballs. The designations bore only an approximate relationship to the actual weight of the projectile when it was applied to modern artillery.

The table below lists the metric and Imperial calibres of various British weapons, which utilised the standard after 1919:

Name	Type	Calibre
		Metric	Imperial
Ordnance QF 1 pounder "pom pom"	Infantry gun/AA gun	37 mm	1.457 inch
Ordnance QF 2 pounder	Anti-tank gun	40 mm	1.575 inch
Ordnance QF 2 pounder "pom pom"	Anti-aircraft gun	40 mm	1.575
Ordnance QF 3 pounder Vickers	Naval gun	47 mm	1.85 inch
Ordnance QF 6 pounder	Anti-tank gun	57 mm	2.244 inch
Ordnance BL 10 pounder Mountain gun	Mountain gun	69.8 mm	2.75 inch
12 pounder (multiple types)	Light field gun	76.2 mm	3 inch
Ordnance QF 13 pounder	Light field gun	76.2 mm	3 inch
15 pounder (multiple types)	Field gun	76.2 mm	3 inch
Ordnance QF 17 pounder	Anti-tank gun	76.2 mm	3 inch
Ordnance QF 18 pounder	Field gun	83.8 mm	3.3 inch
Ordnance QF 20 pounder	Tank gun	83.8 mm	3.3 inch
Ordnance QF 25 pounder	Gun-howitzer	87.6 mm	3.45 inch
Ordnance QF 32 pounder	Tank gun	96 mm	3.78 inch
Ordnance QF 60 pounder	Heavy field gun	127 mm	5 inch

Terminology

When used with British standard nomenclature:

• BL is short for "Breech Loading";
• ML is short for "Muzzle Loading";
• PR is short for "Pounder", e.g. 20 Pounder can be shortenned to "20-PR";
• QF is short for "Quick Firing", indicating the weapon is breach-loaded using cartridge casings, allowing faster loading and firing..

See also

• Pounds as a measure of cannon bore

References

• Rottman, Gordon L.: Elite 124 - World War II Infantry Anti-Tank Tactics, Osprey publishing, ISBN 1-84176-842-1 p. 16