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Ordnance BL 6 inch 80 pounder Mk I
6 inch gun from HMAS Protector at Birkenhead Flickr 6055910302.jpg
Gun from HMAS Protector at Birkenhead, South Australia, August 2011
Type Naval gun
Coast defence gun
Place of origin United Kingdom
Service history
In service 1880 - 19??
Used by Royal Navy
Australian Colonies
Production history
Designer Elswick Ordnance Company
Manufacturer Elswick Ordnance Company
Variants Mk I
Weight 80 or 81 cwt (4 tons)[1]
Barrel length 153 - 156 inches[2]

Shell 80 pounds (36.29 kg) Palliser, Shrapnel, common
Calibre 6-inch (152.4 mm)
Breech 3 motion interrupted screw. Elswick cup obturation
Muzzle velocity 1,880 feet per second (573 m/s)[3]
Maximum range 8,000 yards (7,300 m)

The BL 6 inch 80 pounder gun Mk I was the first generation of British 6-inch breechloading naval gun after it switched from muzzle-loaders in 1880. They were originally designed to use the old gunpowder propellants.

Mk I 80-pounder

6-inch 80-pounder 80 cwt gun

Mk I of 80 cwt (4 tons) as originally built was an Elswick Ordnance design which was weakly made and fired only an 80-pound projectile. It consisted of a steel barrel with wrought-iron coils shrunk over it. A few guns were issued to the Royal Navy but most were replaced by the later versions. Mk I guns remaining in British service were rebuilt with "chase hoops" added around the barrel for strengthening, and the barrel was shortened by 3 inches to keep its centre of gravity at the trunnions. This resulted in the 81 cwt Mk I gun.[4]

The breech was rotated to the left to lock it, unlike standard British service BL guns made by the Royal Gun Factory which all rotated to the right to lock.

These guns are commonly referred to as "6-in. 81-cwt B.L.R." in contemporaneous publications such as Brassey's Naval Annual. The official designation in British ordnance manuals was "80-pounder BL" to differentiate it and its ammunition from the later marks of 6-inch BL guns which fired 100-pound projectiles.

80-pounder in Australian colonial service

Australian colonies and New Zealand purchased various 6-inch guns direct from the manufacturers, usually Elswick Ordnance Company, and these versions do not correspond directly with the official "Marks" as adopted by the British government. Specifications of guns purchased by Australian colonies are similar to those of the original British Mk I 80 cwt gun, firing an 80-pound projectile.[5]

Quarterdeck of Protector with aft 6-inch gun trained to port, circa. 1903

The gun equipped some gunboats of the Australian colonial navies :

Also on armed harbour vessels in Victoria :[6]

  • Gannet : tug
  • Batman : hopper barge / dredge
  • Fawkner : hopper barge / dredge


See also

Surviving examples

Notes and references

  1. 80 cwt as originally made; 81 cwt includes additional weight of hoops added to strengthen the guns. Treatise on Service Ordnance 1893; Text Book of Gunnery 1902
  2. Text Book of Gunnery 1902, Table 12 page 336
  3. Mk I "80 cwt 80-pounder" gun, firing a 78.44-pound projecile, using 34 lb S.P. (gunpowder) propellant. "List of Service Ordance 1891, corrected 1892" in Brassey's Naval Annual 1894
  4. Treatise on Service Ordnance, 1893, pages 257–265
  5. The Victorian Navy manuals of 1887, 1890 and 1895 quote an 80 cwt gun with a bore 156 inches, firing an 80-pound projectile (Shrapnel), 78lb 7oz (Palliser), 75lb (Common) or 77lb (segment) with muzzle velocity of 1880 ft/sec, using a 42-pound Pebble (gunpowder) "Full" or 30lb Pebble "Reduced" charge, which matches the Mk I gun specifications. Some tables in these manuals refer to the 42-pound charge as a "Battering" charge and the 30-pound charge as "Full" charge. Maximum range of 7,200 yards at 13° 5" elevation firing an 80-pound projectile with a 42-pound gunpowder charge.
  6. Victorian Naval Forces General Manual, 1890 from Friends of the Cerberus website


External links

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