Why the Chicago Piano could not be fixed for wartime air defense

What would it take to fix all the problems of the Chicago Piano anti-aircraft gun?

Mechanical repairs would leave the small projectile and fire-control limitations, so an established 40 mm replacement offers the practical wartime solution.

The 1.1-inch Chicago Piano's small projectile is a central limit even if its mechanism can be improved. Effective use of such a small round would require a rate of fire and radar-directed powered control beyond the system available in the 1940s. Enlarging the weapon toward 30 mm raises the question of why the navy should stop there when mature 40 mm alternatives already exist. The pom-pom provides a comparison because its mechanism had undergone a long series of changes from its Maxim ancestry. Replacing the Chicago Piano with a larger, established weapon therefore offers the more practical wartime solution.