Смертоносней быть не может: мортира Маллета

и как далеко?

В Википедии написано: Testing began on 19 October 1857 with further testing on 18 December 1857, 21 July 1858 and 28 of July 1858.[3] Each test was brought to an end by damage to the mortar.[3] A total of 19 rounds were fired with a rate of about 4 shells an hour being achieve
То есть стреляла со скоростью 4 выстрела в час. В людей из нее никогда не стреляли.