BL 6-inch 80-pounder gun

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.

Ordnance BL 6-inch 80-pounder Mk I
TypeNaval gun
Coast defence gun
Place of originUnited Kingdom
Service history
In service1880–1943
Used byRoyal Navy
Australian Colonies
Production history
DesignerElswick Ordnance Company
ManufacturerElswick Ordnance Company
VariantsMk I
Specifications
Mass80 or 81 cwt (4 tons)[1]
Barrel length153 – 156 inches[2]
Shell80 pounds (36.29 kg) Palliser, Shrapnel, common
Calibre6-inch (152.4 mm)
Breech3 motion interrupted screw. Elswick cup obturation
Muzzle velocity1,880 feet per second (573 m/s)[3]
Maximum firing range8,000 yards (7,300 m)

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

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]

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

Ammunition
  • Common shell diagram
  • Full charge (top) and reduced charge (bottom) powder cartridges

See also

Surviving examples
  • A 4-ton 80-pounder gun[7] at Fort Glanville, Adelaide, South Australia
  • A 4-ton 80-pounder gun[8] in Bundaberg Botanic Gardens, Bundaberg, Queensland Australia
  • A restored gun from HMAS Protector is outside the Naval Reserve Cadets building in Jenkins Street, Birkenhead, Adelaide[9]
  • The aft gun from HMQS Paluma is in the Treloar Centre at the Australian War Memorial, in Canberra

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
  7. "6-inch 81 cwt B.L (80-pdr)". Flickr – Photo Sharing!.
  8. "AMMS Brisbane". ammsbrisbane.com.
  9. http://home.iprimus.com.au/artillerist/naval_ss.html

Bibliography
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