| Ordnance BL 6-inch 80-pounder Mk I | |
|---|---|
 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 | 1880–1943 |
| Used by | Royal Navy Australian Colonies |
| Production history | |
| Designer | Elswick Ordnance Company |
| Manufacturer | Elswick Ordnance Company |
| Variants | Mk I |
| Specifications | |
| Mass | 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 firing 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.
- ^ 80 cwt as originally made; 81 cwt includes additional weight of hoops added to strengthen the guns.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
- ^ Text Book of Gunnery 1902, Table 12-page 336
- ^ 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