Printed mine with a 0.8mm nozzle and 0.2mm layer height.
Supports were deactivated without problems, the space in the model is not needed anyway.
Careful with tightening of the screws, they will interfer with the magazine if tightened too much.
I did all my changes in PrusaSlicer, and they are there in the 3MF-file if someone wants to tweak it some more.
The author remixed this model.
Streched overall length so holes will match the frame of a Umarex Colt Special Combat softair gun.
Also bigger cutout for magazine release.
And changed bottom cut on left handle, they did not match in the original.