Grant Hammond is best known (to the extent he is known at all) for a .45 caliber pistol submitted to US military trials in 1917 and 1918. This pistol is a proof of concept prototype embodying some of the concepts that would go into the later .45 caliber pistol, and also showing some concepts that would not see further use. This .32 ACP prototype features a hybrid blow forward / blowback mechanism in which the slide uses a gas trapping system to move forward and the bolt moves backward. It also has a unique system for automatically ejecting the magazine when empty. Truly one of the most mechanically unusual pistols I have ever seen.
US Patent 1138377 (Grant Hammond, “Firearm”, Jul 16, 1913)