Philadelphia inventor Jones Wister conceived a curious weapon in 1916:

One object of the invention is to so construct a fire arm that it can be used in a trench with the aid of a periscope without exposing the soldier to the fire of the enemy. This object I attain by curving the outer end of the barrel so as to deflect the projectile in a direction at an angle to the longitudinal line of the fire arm.

Germany experimented with a similar design during World War II and found that the barrel gave out very quickly under the enormous stress; the bullets sometimes shattered. Wister had envisioned that the same principle might be used with machine guns and even cannon — let’s hope he didn’t try that out.