Volume Twelve - Pre-Victorian to the Present Day - further aspects - Defence of the Realm - Penarth Head Fort and Coastal Battery . . .

The 6-inch Mark VII Coastal Defence Gun - As the 1890's moved on, foreign navies produced bigger and better ironclads. The 6 inch coastal guns were rapidly being outstripped, in that the heavier amour being deployed could no longer be penetrated, and it became necessary to develop more powerful guns. Vickers, Son & Maxim were asked to produce a design showing a substantial increase in performance over the Mark VI, and duly produced their design 763G which was approved for service as the Mark VII in 1898.

This was increased in length by 15cal and provided with a much heavier propelling charge, giving a muzzle velocity of over 500 feet per second. This in turn led to a welcome increase in penetration performance. With its 100 lb.shot delivering 4,300 foot-tons, the Mark VII gun could pierce 15 inch of plate at 1,000 yards, against the Mark VI gun's 2,400 foot-tons and 11 inch penetration at the same range. In later years, provided with a capped shell, it could pierce 1cal of Krupp Cemented Armour at 2,950 yards.

In addition to this increase in performance, the rate of fire was improved by the adoption for the first time of the 'Pure Couple' single-motion breech mechanism and the Welin breech screw, allowing the breech to be opened and closed in a fraction of the time needed for the earlier three-motion mechanisms.

A shot-guide was linked to the breech, so that the screw came clear of the breech opening the guide slid into place to speed up the loading and prevent the shot from injuring the breech threads.

Numbers of these guns were also supplied to the Navy for ship mounting ; the only difference between Naval and Land service guns lay in the rifling. For some obscure reason the Naval guns were rifled straight from the breech to 211.06 inch from the muzzle, thereafter increasing to one turn in 30cal, while the Land Service guns were rifled straight to 198.8 inch and then began their increasing twist. In 1902 sanity prevailed, and all guns were rifled on the Naval plan but with 36 grooves instead of the original 24.

These guns remained in service in all parts of the country until their final withdrawal in 1956-59. Among other locations, they were installed in the Heugh and Lighthouse Batteries in Harplepool, where they were engaged against the German armoured cruiser attack in 1914.