Relatively rare, and rather expensive.
the Maxim machinegunMaxim machine gun.
Machine gun is a much broader category, which includes both current and obsolete models. The Maxim gun is a specific type of machine gun, and an obsolete one, at that.
Hiram Maxim
1844
Hiram Maxim
Hiram Maxim
Hiram Maxim invented the Hiram machine gun
Sir Hiram Maxim.
Hiram Maxim
The first true machine gun was invented by Hiram Maxim in the United Kingdom.
Maxim
Invented, not invited. Hiram Maxim.