From this: http://cs.finescale.com/fsm/modeling_subjects/f/7/p/1636459/reply.aspx?tsid=8518b6d4-cd4f-4375-af55-a51d5b328642
ARMY LIGHT TANK is unloaded from its landing craft during joint Army-Marine amphibious exercises at New River, N.C. in August 1941. (SC 125129)
Before the reports of the New River exercises had been received by the Navy Department, a contract had been let for 131 additional tank lighters. These were of a 47-foot Bureau design, a prototype of which had never been built. As a result of the good showing of the Higgins tank lighter at New River, this contract was later reduced to ten. Higgins was the low bidder, and built one craft to Bureau specifications, although he was convinced that the design was unseaworthy. His fears proved to be well founded when the tests were carried out. By this time, however, the tank lighter program had again changed direction.
On October 1941, the Auxiliary Vessels Board of the Navy had reported that there was no lighter capable of landing the newly developed Army 30-ton medium tank. The Secretary of the Navy directed the Bureau of Ships to remedy this deficiency. Accordingly, in December existing tank lighter contracts were changed to provide 50-footers in lieu of the 45-foot Higgins and 47-foot Bureau types still to be built. Both Higgins and the Bureau produced designs of 50-foot craft. Before any deliveries could be made, President Roosevelt, at a White House Conference on 4 April 1942, directed the procurement of 600 additional 50-foot tank lighters by 1 September for the North African operation. The Bureau of Ships, to meet this commitment, ordered 1,100 of it own design.
Since this order was earmarked for service in a projected Army operation, the Army showed keen interest in a test of the two types held near Norfolk on 25 April 1942. Each carried a 30-ton tank, elaborately lashed down in the Bureau lighter, merely blocked in place in the Higgins. Wind velocity ran 18 to 23 miles per hour, with wave heights estimated between 1 1/2 and 2 feet. Both lighters showed a speed of 10 miles an hour over a measured 1 1/2-mile course. What happened after that is described by the Army observer who made the trip in the Higgins type:
As we neared the [antisubmarine] net it became apparent that the Navy Bureau-type tank lighter was in trouble. She appeared to have a tendency to dive when headed into the seas and was taking considerable water aboard. She stopped several times and members of the crew could be seen manning hand pumps and attempting to better secure the tank in the lighter. Once when under way and making a wide turn, it appeared that the lighter was going to overturn. Some of the crew was seen straddling the higher bulwark and the coxswain had left the pilot house and was steering the vessel from the rail.
While this was going on, our [Higgins] lighter was standing by, as was a picket boat and two
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Higgins 30-foot boats. None of these vessels was experiencing and difficulty. The Higgins tank lighter was maneuvering around in sharp turns into the sea, through the wave troughs.
We then [after Bureau lighter turned back] opened the engines up to 1,900 r.p.m. and proceeded past Little Creek to Fort Storey. The lighter took no water except a little spray. Performance was excellent in all respects. The lighter was beached in the surf and the tank ran off onto the beach despite poor handling by the coxswain who finally allowed the lighter to broach to. In spite of this the vessel had such power and retraction qualities [as] to get back into deep water.
As far as comparison of characteristics of the types of tank lighters are concerned, it may be stated that in the May 25 test there was no comparison.
As a result of these tests, the Bureau hastily notified all yards to shift to the Higgins type. Thus the Higgins 50-footer became the standard tank lighter of the Navy, the prototype of the LCM (Landing Craft, Mechanized) as the Marines knew it in World War II, and as they know it today in enlarged form.