Historic context :

The American inventor Samuel Neal McLean was one of the pioneers of the modern armaments, since he was the one patenting in 1902 the very first automatic weapon system taking its energy from a piston using the shooting propulsive gasses. Although this system never reall worked on its firm Mc Lean Company's machineguns projects before it associated with the colonel Issac Lewis and designe the famous Lewis machinegun that equipped the British Army during WWI, it was a bit more easily used on a small 37 mm gun.

This automatic gun that was supposed to allow incredible firing rates of about 100 rounds per minute ws not able to convince the US Army and the US Navy during numerous tests and demonstrations between 1903 and 1910 on the models MkI, then MkII, showing too much reliability issues. But in 1916 the Poole Engineering Machine Co, from Baltimore, manufactured a new variant named the '37 mm McLean MkIII' that was keeping the long 54 calibres barrel and the pneumatic automatic system of the MkII version never accepted by USA, but mounted on a tubular carriage similar to the one made by Bethlehem Steel for its landing gun.

258 such guns were built, and 218 of them delivered to Russia before that nation withdrawed from war in 1917. The remaining guns were again proposed to the US Navy without success. Russia kept its guns in the Army inventories until 1935 when most of them were given to Spain. Czechoslovakia during the fights against the Soviets in 1919, and Filand during the Winter War in 1939 captured some of these guns and used them too.

Technical data :

• Complete description : 37mm Mc Lean Automatic Cannon MkIII
• Design year : 1916
• Calibre : 37.20 mm
• Weight in firing position : 336 kg
• Weight for transportation :
• Tube length in calibres : 54.00
• Grooves : 0 inconnu
• Projectile weight :
• Initial speed : 442 m/s
• Fire rate : 100 rounds / minute
• Range : 3200 m
• Elevation range : unknown
• Direction range : unknown

• A gun for all nations - The 37 mm Gun and Ammunition - Volume II - 1914-1926           Robert A Mellichamp                     2012