the most powerful coastal guns used at krepost sveaborg were the 45 caliber model 1891 guns. they had a maximum range of but suffered from primitive mountings: the heavy guns, weighing , were completely hand-operated resulting in slow traverse and elevation rates and exhausting the gun crews. the rate of fire was only one shot every two minutes and they were also not capable of penetrating the armour of newer warships: at the range of they could penetrate of armour at 90° angle. first four guns were transported to the fortress in 1913 from kronstadt fortress, two guns each from constantin and obrutshev forts. twelve guns were transported from vladivostok in 1914 and eight more arrived in 1915, with a total of 24 guns in six four-gun batteries. these guns formed the primary armament of the sea front main line of defence. the batteries were located on rysäkari, katajaluoto, kuivasaari, isosaari (two batteries) and itä-villinki.