4. The Chauchat
First manufactured for the French army in WWI, the Chauchat has actually become known as the worst light machine gun to date. Not only did the bolt find itself locking in place when it got overheated, but the gun was effectively unusable thereafter until the metal would cool, and reform to its original size.
Unfortunately, the Chauchat’s bad design of an oddly-shaped, curved magazine and large cutouts that caused jamming in muddy trenches made it a horrible, flawed weapon. Furthermore, troops were in danger of hurting themselves because the mechanism could hit the user in the face. So not only was the Chauchat overly complicated, but the quality of manufacturing left something to be desired.