A 1935 self-propelled Long Tom meets the chassis problem

What if the US Army began developing a self-propelled 155 mm Long Tom gun and howitzer in 1935?

It could become powerful mobile artillery, but only after a difficult program built a long, heavy, purpose-designed chassis around the weapon.

The proposed vehicle combines the Long Tom's gun role with self-propelled howitzer work, but the barrel and recoil system are difficult to fit onto a 1935 chassis. The panel expects a long development program because no normal contemporary tank offers enough length and load-bearing margin. An M6-scale hull with a rear casemate is suggested as the most plausible American arrangement if the project is forced through. Later British experimental vehicles help illustrate the shape of the solution, but they also show how far the necessary chassis technology still had to mature. A working design would give the United States powerful mobile artillery and could prompt foreign imitators. Its usefulness therefore depends less on the gun itself than on solving transport, recoil, and automotive integration.