▁with ▁a ▁central ▁jack ▁to ▁raise ▁the ▁gun ▁during ▁traverse ▁and ▁to ▁take ▁some ▁of ▁the ▁enorm ous ▁weight . ▁ ▁The ▁main ▁bar rel ▁of ▁the ▁K 5 ▁is ▁ ▁in ▁cal ib re , ▁and ▁is ▁rif led ▁with ▁twelve ▁ ▁gro ov es . ▁These ▁were ▁originally ▁ ▁deep , ▁but ▁were ▁made ▁shall ower ▁to ▁rect ify ▁crack ing ▁problems . ▁ ▁History ▁The ▁K 5 ▁was ▁the ▁result ▁of ▁a ▁crash ▁program ▁launched ▁in ▁the ▁ 1 9 3 0 s ▁to ▁develop ▁a ▁force ▁of ▁railway ▁guns ▁to ▁support ▁the ▁We hr macht ▁by ▁ 1 9 3 9 . ▁K 5 ▁development ▁began ▁in ▁ 1 9 3 4 ▁with ▁first ▁testing ▁following ▁in ▁ 1 9 3 6 ▁at ▁Dar low o ▁( G erman : ▁Sch ieß platz ▁R ü gen wal de - Bad ) ▁in ▁the ▁former ▁Far ther ▁P omer ania ▁at ▁the ▁South ▁coast ▁of ▁the ▁Balt ic ▁Sea . ▁Initial ▁tests ▁were ▁done ▁with ▁a ▁ 1 5 0   mm ▁bar rel ▁under ▁the ▁design ation ▁K 5 M . ▁ ▁Production ▁led ▁to ▁eight ▁guns ▁being ▁in ▁service ▁for ▁the ▁In vas ion ▁of ▁France , ▁although ▁problems ▁were ▁encountered ▁with ▁bar rel ▁splitting ▁and ▁rect ified ▁with ▁changes ▁to ▁the ▁rif ling . ▁The ▁guns ▁were ▁then ▁reliable ▁until ▁the ▁end ▁of ▁the ▁war , ▁under ▁the ▁design ation ▁K 5 ▁T ief zug ▁ 7   mm . ▁Three ▁of ▁them ▁were ▁installed ▁on ▁the