This is a static model about 40cm high with room for electronics, it is the same size as this movable tracking model from which also contains instructions on how to make the legs: http://www.instructables.com/id/Building-a-moving-and-tracking-Portal-Turret/
I made it from screenshots from in the game and some things are optimized or removed to be printable.
There are extra parts for the guns that have been made with extra clearance, and the split ammo box for gluing to the shell.
The shell, dividers and the side panels have holes for 1.75mm filament as locating pins.
Many parts require supports as you can only optimize so much before taking away too much and altering the look too much, only two wires on the middle part were removed and the bottom part was redesigned to fit the legs from the moving turret design.
The legs require 3mm aluminium sheet metal and 4mm stainless steel rods, the guns and side panels are supported by an 115mm long aluminium tube 8mm in diameter.
There is plenty of space to put electronics inside and in the gun barrels you can put 5mm LEDs. The part bottom 2 has a hole for powering any electronics you put inside, but I have not printed it.
The ammo box and middle is available as as one piece or split into halves.
The bottom part also has a second file that has a hole for cable.
The guns has an extra loose version that can be used in case the regular part is too tight to fit on the side panels.
The author marked this model as their own original creation.