 The ship also participated in the main attack on the Dardanelles forts on 18 March . This time a 6 @-@ inch ( 152 mm ) howitzer battery opened fire on Agamemnon and hit her 12 times in 25 minutes ; five of the howitzer shells hit her armour and did no damage , but the seven that hit outside her armour protection did considerable structural damage and temporarily put one of her 12 @-@ inch ( 305 @-@ mm ) guns out of action . 
