Semi vs Full Automatic

Semi vs full-auto is a conversion that should almost not need further definition however there seems to be a huge amount of misinformation floating around the subject.

The prefix semi- refers to “half” or “less than full”.  So, by simple definition semi-automatic would refer to a weapon that is less than full-automatic.  Yet, many conversations and even news agencies tend to treat them the same.


Here is the simple answer.  Semi-automatic refers (when talking about firearms) to a weapon that is able to self load.  However it is not capable of full-automatic fire.  When the user pulls the trigger a single round is fired.  As the weapon cycles its mechanism the spent case is ejected and a new cartridge is placed into the firing position.  The new cartridge WILL NOT fire until the user full removes pressure from the trigger and then pulls the trigger again.  At this time the entire process continues.  A semi-automatic rifle CANNOT be correctly identified as a machine gun.

A semi-automatic pistol firing, ejecting the spent casing, and self loading the next cartridge. Image owner unknown.


Full-automatic weapons usually (but not always) have a semi-auto function but also have an additional select-fire setting that allows the user to hold the trigger down.  The weapon then cycles continuously until the trigger is let go or the magazine runs empty.

Which is legal in the United States?


When was full-automatic made illegal in the USA?


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