 The fort 's main armament were the two RML 10 inch 20 ton guns — Numbers 3470 and 3472 . They were manufactured in 1879 by WG Armstrong and Company and originally used the Armstrong protected barbette loading system . They were made to the 1878 pattern and supplied on traversing slides . The guns have a 10 @-@ inch ( 250 mm ) calibre , a range of 6 @,@ 500 yards ( 5 @,@ 900 m ) with a muzzle velocity of 1 @,@ 630 feet per second ( 497 m / s ) and are capable of penetrating 11 inches ( 28 cm ) of iron at 2 @,@ 000 yards ( 1 @,@ 800 m ) . 
 The fort <a href='null_genetive' title='1'><mark>'s</mark></a>main armament <a href='uninflect' title='2'><mark>were</mark></a> the two RML 10 inch 20 ton guns — Numbers 3470 and 3472 . They <a href='uninflect' title='3'><mark>were</mark></a> manufactured in 1879 by WG Armstrong and Company and originally used the Armstrong protected barbette loading system . They <a href='uninflect' title='4'><mark>were</mark></a> made to the 1878 pattern and supplied on traversing slides . The guns <a href='got' title='5'><mark>have</mark></a> a 10 @-@ inch ( 250 mm ) calibre , a range of 6 @,@ 500 yards ( 5 @,@ 900 m ) with a muzzle velocity of 1 @,@ 630 feet per second ( 497 m / s ) and <a href='drop_aux' title='6'><mark>are</mark></a>capable of penetrating 11 inches ( 28 cm ) of iron at 2 @,@ 000 yards ( 1 @,@ 800 m ) . 
The fort  main armament was the 2 RML 10 inch 20 ton guns — Numbers 3470 and 3472 . They was manufactured in 1879 by WG Armstrong and Company and originally used the Armstrong protected barbette loading system . They was made to da 1878 pattern and supplied on traversing slides . The guns got a 10 @-@ inch ( 250 mm ) calibre , a range of 6 @,@ 500 yards ( 5 @,@ 900 m ) w a muzzle velocity of 1 @,@ 630 feet per second ( 497 m / s ) and capable of penetrating 11 inches ( 28 cm ) of iron at 2 @,@ 000 yards ( 1 @,@ 800 m ) .