See this thread:
http://www.tank-net.com/forums/index.ph ... opic=39110
They quote a passage from Ian Hogg's "Encyclopedia of Infantry Weapons of WW2" below --
37mm Manpack guns
Although few of these weapons saw service and full specifications for them are not available, the development, like that of the British 95mm, is not without interest, as it shows the measures to which the US Army were prepared to go in order to get firepower well forward in jungle warfare.
The proposal for these weapons seems to have arisen late in 1943, after experience in the Pacific area, and in November 1943 a project was begun to develop a light 37mm gun which could be dismantled easily and quickly to be carried among the members of the infantry squad. The chamber was to take the short (5.69in) cartridge of the M4 aircraft gun, and, working at a chamber pressure of 27,000lbs per square inch, it was predicted that it would be able to fire a high explosive shell at 1500 feet per second. A case-shot anti-personnel round was to be developed, and the entire gun and mount (a modified machine gun tripod) was to weigh 250lbs. Within six weeks a pilot model was built; 200 were ordered but the trials of the pilot showed it to be unstable on its mounting, so the order was suspended while a redesign was begun. In January 1944, with the re-design complete, authority was given for the limited procurement of 200 'Guns 37mm T32' as they were known with the povisio that further development would depend on what the user thought of it.
By July 1944 155 guns had been sent to the Central Pacific area and the procurement order had been increased to 455 equipments, but that appears to have been the end of development of that model. In June 1945 the procurement authority was cancelled since, 'there have been no Theatre requests for extra consignments' . . . Apparently the users didn't think a great deal of it.
Meanwhile in April 1944 work had begun on a T33 model. This was of similar characteristics to the T32 but much lighter; the gun was to weigh 75lbs instead of the T32's 106lbs. When it was finally built, however, this target was not reached, the weight coming out at just under 1001bs. Twelve guns were made, but by the time they were completed the 57mm recoilless gun was ready for issue; since this delivered a heavier shell and weighed a lot less, the infantry preferred it and the T33 project was terminated in September 1945
IIRC, a manpack 37mm gun was taken to Iwo Jima by the U.S. Army's 147th Infantry regiment which garrisoned the island after the Marines left.
A short story on the 147th at Iwo Jima is at this link, minus any mention of 37mm guns, unfortunately --
http://lesterstaube.com/147Infantry.html
