U.S. PGM designs are compared with the operational demands of fast torpedo craft. PGM-9 carried a three-inch dual-purpose gun, a twin 40 mm mount, six 20 mm guns, machine guns, and rockets, yet its roughly 20-knot speed forced the Navy to shift it from PT-boat support to minesweeping support. The postwar PGM-39 class was slower still at about 17 knots, while the later Asheville class finally combined economical diesel cruising with turbine-powered speed above 40 knots. A support gunboat did not need to match every instant of a PT boat's maximum dash, but it needed enough speed to enter and withdraw with the formation. A heavily armed river gunboat and an oceanic fast-attack escort posed fundamentally different design problems.
Notable Point · 2:34:21-2:46:21
U.S. PGM speed problem and PT boat support
The late comparison argues that American patrol gunboats had firepower but not the speed needed to support fast PT-boat operations.