4 walls, 15% infill should work, the pusher does need supports, and you will need a small o-ring to go on the pusher head. the pusher goes in place of the standard breech, but the barrel assemblies have different assemblies as follows; for the brass dart gate, flare one end of your 17/32 brass tube, stick the non-flared end through the chamfered side until it seats, then insert into the original dart gate through the front of the blaster. for the standard dart gate, insert a 16mm/ 5/8ths barrel into the larger side, secured with some sort of glue, then slide into the original dart gate through the front of the blaster. you may need to play with scaling in your slicer a little bit to get these to work. and the dart gates should be a tight fit in the original dart gate, and should not move upon priming the blaster forward. I would also recommend sealing the plunger tube, and increasing the spring load in addition to adding some teflon under the o-ring on the base of the pusher to get an optimal seal. I was able to get my build up to 160 fps average with a stupid light prime.
Video by DR Flux (yippee)
The author marked this model as their own original creation.