Armorer
A certified professional who works on guns. Armorers repair, enhance and sometimes build guns.
Automatic
Fully Automatic - a firearm that continues to fire (repeatedly) until the trigger is released.
Examples of fully automatic handguns include the Glock 18 which, like all fully automatic weapons, is not available to the public in the United States.
Semi-automatics are frequently referred to as “automatics”, a term which really describes a fully automatic weapon.