Fully automatic firearm

An automatic firearm continuously fires rounds as long as the trigger is pressed or held and there is ammunition in the magazine/chamber. In contrast, a semi-automatic firearm fires one round with each individual trigger-pull.

Although all "semi-automatic", "burst fire" and "fully automatic" firearms are "automatic" in the technical sense that the firearm automatically cycles between rounds with each trigger pull, the terms "automatic weapon" and "automatic firearm" are conventionally reserved by firearm enthusiasts to describe fully automatic firearms. Use of this convention can avoid confusion. Firearms are further defined by the type of firearm action used.

Self-loading firearms are designed with varying rates of fire due to having different purposes. The speed with which a self-loading firearm can cycle through the functions of:

is called the cyclic rate. In fully automatic firearms the cyclic rate is tailored to the purpose that the gun is made to serve. Anti-aircraft machine guns often have extremely high rates of fire to maximize the probability of a hit. In infantry support weapons these rates of fire are often much lower and in some cases variable within the design of the firearm. The MG 34 is a WWII-era machine gun which today would be referred to as a general purpose machine gun. It came in several variations with a cyclic rate as high as 1200 rounds per minute, but also made an infantry model which fired at 900 rounds per minute.

Firing any firearm generates a very high temperature in the firearm's barrel and elevated temperature throughout much of its structure. If fired too fast, the components of the firearm will suffer a structural failure. This means that all firearms, regardless of whether they are semi-automatic, fully automatic, or burst mode in their firing methods, will overheat and fail if fired too often. This is especially a problem with fully automatic fire. In actual use (for example: the MG34), a gun might be able to fire at 1200 rounds per minute, but in one minute it may also overheat and fail. So guns used in a repeated firing mode must not be fired too often. The MG34 is fired manually in bursts of 5 to 7 rounds (no automatic disconnector mode in this gun). It can fire at an effective rate of 150 rounds per minute.

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