These guns were developed to exploit the new "QF" technology, which involved loading the propellant charge in a brass case with integrated primer in its base.

The brass case sealed the breech, allowing a lighter mechanism, and at the same time disposed with the necessity of washing or sponging any smouldering fragments left from the previous shot, which could ignite the charge (then of black powder) prematurely.

The breech mechanisms were developed from the existing 6-inch (150 mm) BL mechanisms, but as it no longer had to provide obturation (sealing of the breech), the front was made coned rather than straight which allowed it to be swung round to the side before it was fully withdrawn, rather than having to be fully withdrawn before swinging to the side as with the BL gun.

[3] The preceding generation of British 6-inch guns (BL Mks III, IV and VI) had old-style trunnions by which they were mounted on Vavasseur inclined slides to absorb recoil.

The pre-dreadnought battleship classes of the Royal Sovereign-class (including the turreted HMS Hood-class, Centurion-class, Majestic-class and Canopus-class ships carried up to 12 guns.

During the Second Boer War one gun was brought ashore fromHMS Terrible in Natal in February 1900 at the request of General Redvers Buller, presumably[citation needed] in response to the failure at Colenso.

[7] The 7-ton weight (compared to the 2½ tons of the Boer 155 mm "Long Tom") meant that it was effectively immobile on the battlefield and could not be moved forward to shorten the range.

[11] In World War I Britain urgently needed heavy artillery on the Western Front, and various obsolete 6-inch naval guns were converted to 8-inch howitzers.

It was further re-named in centimetres on 5 October 1917 as part of the standardisation process for the Imperial Japanese Navy converting to the metric system.

The Type 41 6-inch (150 mm) gun fired a 100 lb (45 kg) shell with either an armour piercing, high explosive or general purpose warhead.

[14] These guns were adopted in very limited quantity by the United States Army Coast Artillery Corps as part of the Endicott period fortifications, and were initially mounted 1898–1907.