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1.
Any firearm built of after market parts. Usually used to refer to AR-15's or 1911's/clones. Common practice for shooters who like to "roll their own" so to speak.
a: Dude sweet AR, what kind is it?
b: Its a Bushmaster lower, Olympic upper and a DPMS barrel.
a: So its a franken-gun?
b: Yeah.
by budgieramone January 15, 2004
 
2.
Derived from Frankenstein's Monster. This is a gunsmith's term meaning a firearm made from parts of the same model, but different manufacturers.
Example; a 1911 Frankengun- Essex or Caspian frame, Colt slide, Lothar-Walther barrel, Wolf springs, Brownells pins, Wilson Combat trigger, sear, and hammer, Ed Brown barrel link, mainspring and housing, and beavertail, George Heinie oversized safety and slide catch. Topped off with Millet or Novac sights.
Anybody who doesn't know what a Frankengun is is "Boot".
Most gunsmiths who build custom guns are usually building a frankengun.
by ghost3x7 April 21, 2009
 
3.
1. A firearm that does not exist.
2. A firearm consisting of several different gun parts and does not exist.

n.
Derived from the word "Frankenstein".
n 1. The ZF-1 created by Zorg in the movie "The Fifth Element" is the ultimate frankengun.

2. My nephew made his very own frankengun to show off.
by Joe Black February 16, 2005