Summary This is a Plug&Play breech mod for the Nerf Falconfire blaster. It contains two barrel holder, one for the front and one for the back. The upper side of the holder is marked with an "O", because the hole is not in the middle on the vertical axis. The barrel i use is a K&S 9/16 inch (inner diameter 13,49mm, outer diameter 14.29mm). The breech adapter is glued to the pusher, where the dart normally is inserted. I upload two versions of the adapter, with different diameters for the o-ring fitment. You might need to try both with your barrel, before glueing it into your pusher. O-ring i used is a 9x2mm (9mm inner diameter and 2mm wire = 13mm outer diameter). Depending on your printers dimensional accuracy, you might need to sand the parts. For the glue, i use a flexible glue like "Shoegoo". Because it seals very good, and ( if needed) can be removed without breaking parts. You have to remove the mechanism (which holds the dart back when sliding the primer to the front) in front of the blaster, where the rear holder be sitting. And on the pusher, the little "nose" in the very front has to be cut. With this conversion the Falconfire with stock spring already has good accuracy and power. I also upload a spring spacer for a little bit more power. Do not sell any of these parts commercially on any way. Cheers, Harun Print Settings Notes: I recommend 100% infill on the breech adapter, and using a brim. The holders have no specific settings needed.