Historians count the machine gun among the most important technologies of the past 100 years. As much as any other factor, it set the brutal, unrelenting tone of World War I and World War II, as well as most of the wars since that time. With this machine, one soldier could fire hundreds of bullets every minute, mowing down an entire platoon in only a few passes. Military forces had to develop heavy battle equipment, such as tanks, just to withstand this sort of barrage. This single weapon had a profound effect on the way we wage war.

Photo courtesy Department of Defense
U.S. Marines fire a M-240G machine gun during training exercises at Camp Lejeune Marine Corps Base in North Carolina. Medium machine guns such as this one are an essential element in the modern arsenal.

In light of their monumental role in history, it's somewhat surprising how simple machine guns really are. These weapons are remarkable feats of precision engineering, but they work on some very basic concepts. In this edition of HowStuffWorks, we'll look at the standard mechanisms machine guns use to spit out bullets at such a furious rate.