Print in the orientation provided for best results.
I print these in PETG with 2-3 perimeters and 3-4 bottom/top layers.
I print everything at 20% infill except the barrel and pins, which I print at 60%.
The slide has built in brims and supports which will need to be trimmed away with a hobby knife.
The ejection port has some built in supports as well, but should easily break away.
Insure to remove any elephant foot on your parts - especially on the barrel.
The barrel should move very freely in the slide, without excessive play. Scale the barrel up or down slightly if you have issues.
You may also need to scale the pins up or down slightly as needed to get the right amount of friction fit.