I've been threatening for awhile to make one of these.

This is an OTB (over the barrel) mock suppressor that will fit up to 20mm outer barrel OD, with 14mm CCW threads about 65mm deep.

I remixed the dong from thingiverse (I think), using 3D Builder. Place the Z-seam along the bottom of the dong. Not only will it hide the seam, but effectively emulated the male raphe.

Use whatever filament and settings you like for airsoft stuff.