With the lead up to the invasion of Imperial Japan and Nazi Germany in World War II, the U.S. Army needed some serious air support on tap. While there were a number of capable aircraft on hand, such as the P-47 Thunderbolt and the P-51 Mustang, each with a half dozen .50 caliber M2 heavy machine guns, the Army wanted something…bigger. What they got was an aircraft named the Grizzly and this flying bear was, quite literally, a cannon with wings.
Since the airplane took to the sky in 1903 at Kitty Hawk, North Carolina, the U.S. Army had a leg up in flying war machines. It was an Army Captain, Charles de Forest Chandler, who took the first machine gun up on an experimental craft and used it effectively to hit targets on the ground. By WWI, the first .30 caliber belt and drum fed light machine guns went airborne. By 1939, the Germans were flying with 13mm and 20mm cannon, while some U.S. planes (the P-39) carried cannons as large as 39mm.
In 1943, the U.S. Army Air Force in the Pacific took a few B-25 Mitchell bombers and installed a single-shot T9E1 75mm cannon, the same gun used on the Sherman tank, in the front of the bomber, firing through the nose.
The large tube at the front of this B-25 that looks like a sewer drainpipe? Yeah, that’s a cannon.
These huge flying artillery pieces could vaporize enemy planes (it happened at least once) as well as sink Japanese ships with just a few well-placed shots. Of course, the plane lost 40mph airspeed every time it fired, but hey, it was spitting out a 3-inch wide artillery shell.
The B-25G/H models had to have an airman upfront hand-loading the 75mm cannon, which was not very efficient.
These ‘cannon-nosed’ B-25s proved so popular and successful that a special model of the 75mm gun, the T13E1 / M5 , made lighter and especially for use in an aircraft, was produced for the B-25H series bombers. Nevertheless, they still suffered from the fact that they were single-shot weapons, which had to be reloaded, by hand, by an airman heaving shells back and forth through the nose of the cramped bomber. Which was a bear of a problem that led to the Grizzly, and its mother-beautiful semi-automatic M10 75mm gun
Read the rest in my column at Firearms Talk