You'll need some 3mm screws for general assembly, 3mm screw and
nut to make a firing pin.

Barrel takes 8x6mm seamless tube or .22 liner. Glue in the liner and then 
glue in whole barrel into the frame.

Weight block has a compartment to stack one euro cent coins for 
mass adjustment.

Mainspring must have ID greater than 12mm, 
OD lesser than 18.5mm and be at least 84mm long. 
Ideal thickness of wire is yet to be determined, 
but it's somewhere around 1.0-1.4mm. 
Springs from commercial pistols could work too if they're long enough.

Other springs vary from 6 to 13mm in OD, but they can be substituted
as there are no specific requirements for them. Only these conditions must
be met: 
*Trigger return spring should be significantly stiffer than 
disconnector spring.
*Same spring should have enough beef to press down on the 
disconnector while it's dear surface is being pressed down by full weight
of mainspring.

Edges of the magazine have to be sanded down for 
perfect fit - unless your printer is finely calibrated and tuned to 
extreme accuracy.