Since aircraft of the period could not carry large bombs, the burden of delivering heavy firepower fell on the artillery.

Rail transport proved to be the most practical solution, because the problems of weight, mobility and setup time were addressed.

The guns used an interrupted screw breech and fired separate loading bagged charges and projectiles.

During loading the barrel was lowered 6° and a shell was brought forward by a cart[5] that ran on a rail to the breech of the mortar.

[7] The carriage was of simple construction and was made from steel beams that were welded together to form a box with a large hollow center section to allow high angles of elevation.

The recoil system consisted of a U-shaped gun cradle that held the trunnioned barrel and a slightly inclined firing platform with hydraulic buffers on each side.

Normally this type of mount stood behind a cement slab behind a parapet as part of coastal fortifications and they weren't designed to be mobile.

The most time-consuming part of the site preparation included the excavation of a large pit into which the steel firing platform was sunk.

The mortar was then assembled by the gantry cranes which ran on two parallel 60 cm gauge tracks laid 7 m (23 ft) apart, perpendicular to the line of fire on each side of the pit.