Naval gun 37 mm/56. M4 (1942)

[klem]

The Oldsmobile gun (37 mm/56 M4), was developed on the basis of an aircraft gun, originally it was designated under the name of T9. Designation changed to M4 around 1942, it was first used on P-39 aircraft. The distinctive "arched" magazine was designed to fit the nose of these aircraft. Many of these guns were salvaged from crashed planes and installed on PT boats to equip these small craft with a "barge buster" weapon. This proved successful and new guns were produced specifically for use on PT boats. The photographs shows a PT boat armed with a 37 mm cannon fixed to the bow.For more details see here. (http://www.navweaps.com/Weapons/WNUS_37mm-56_m4.php)

 

[Rickshaw]

Did they ever abandon the arched magazine?

 

[athpilot]

The Army´s 2nd Engineer Special Brigade Support Battery modified a number of LVT(A)-2 amtracs to provide fire support. On the stern is a Oldsmobile M4 autocannon taken from a P-39 fighter. In the cargo bay are the rails for a barrage rocket launcher. This vehicle was used to attack Japanese dug-outs on Schouten Island in the Dutch East Indies in 1944. The cartoon on the hull side shows a snorting bull (from the book by Steven Zaloga and George Balin, US Amtracs and Amphibians at War 1941-45).

According to this site the gun could be fed with an 15 rounds arch magazoine or a modified 30 rounds belt. https://www.armedconflicts.com/37-mm-Automatic-Gun-M4-T9-t179803

 

[Colonial-Marine]

There were two derivatives of the 37mm M4 that saw some use, the M9 and M10. The M9 used a more powerful 37mm cartridge, (I think the same as the M1 37mm anti-aircraft gun) and was fitted to the sole P-63D Kingcobra produced and some later PT boats. The M10 was an M4 with minor improvements and could be fed by a 58 round belt. This saw service on most of the P-63 Kingcobras built.

If anyone has any images or information on the PT boats that were fitted with the M9 I'd be interested.

 

[klem]

37 mm automatic gun evolution (Extract)