BL 4-inch Mk I–VI naval gun

The BL 4-inch gun Mk I – Mk VIMk I – Mk VI = Marks 1 through to Mark 6. Britain used Roman numerals to denote Marks (models) of ordnance until after World War 2. This article covers the first six models of British BL 4-inch naval guns were a family of early British breech-loading 4-inch naval guns.

History 13 cwt Mk I, 15 calibres This was the first 4-inch BL gun. With its short (60-inch total) barrel it had a range of only 5,500 yards.DiGiulian

22.5 cwt Mk I, 25 calibres With its longer barrel (100 inch bore) Mk I had a range of 7,200 yards. Both early Mk I types were quickly withdrawn from service following the explosion of a similar BL 6 inch Mk II gun on board HMS Cordelia in June 1891. Mk I 22.5 cwt continued to be used for training.

26 cwt Mks II - VI, 27 calibres The improved 27-calibre Mk II gun and subsequent Marks, often referred to as 4 inch 26 cwt, replaced the early Mk I versions in service. The longer barrel (108 inch bore : 27 calibres) gave it a range of 7,700 yards.Text Book of Gunnery 1902

Mk II guns and later Marks armed the following warships : as re-gunned in 1885 as re-gunned in 1885 Pygmy-class composite screw gunboats of 1888 s launched in 1889 as re-gunned in 1891 s of 1894

The gun was succeeded in its class from 1895 by the QF 4-inch gun Mk I.

QFC 4-inch gun A small number of these guns were converted to QF to use the same cartridges as the QF 4-inch gun. They were designated Mk I/IV, I/VI etc. depending on which Mark of BL 4-inch had been converted. All had a bore of 27.85 calibres after conversion, with a muzzle velocity of 2,177 ft/second.

Surviving examples A gun from 1888 at Explosion! The Museum of Naval Firepower, Gosport from Victorian Forts and Artillery website A gun from HMS Gannet, mounted on top of Calshot Castle at the entrance to Southampton Water from Victorian Forts and Artillery website

BL 4-inch Mk I–VI naval gun

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