The 75 mm gun model 1929 was the first design for a fortress gun for the Maginot Line. It used to standard barrel of the 75 mm field gun, but with a heavier mantle. Like all guns of the Maginot Line it had a special fortress mounting in order to reduce the size of the embrasure. However the main disadvantage of this design was the protruding barrel. The gun model 1929 was only used in the first generation artillery casemates and in the works in the Alps. For more information click here.