SYPR, a SillyShell HYPR

Introduction

Ever since I've built my first HYPR, I wanted to make a break-action “flare launcher” version, yet keeping the single action stringer mechanism. So, this is it, still a WIP project.

Design changes

This kit is a modification of the original HYPR, with the following changes:

• Break-action
  The idea was taken from SillyPilot (v1) and Goblin (v2), implementing a shock-cord loaded ejector, which both retains the shell in barrel, pushes it against the Base and extracts it far enough to be taken out manually.
   

• A single-part Base
  Without the need for an internal barrel, the Base is now a simplified part, which is fixed to both Wunderbar and TopRail with four 3x10mm (4-40) screws.
   

• Shorter plunger and plunger tube
  To keep the blaster as close to original HYPR in terms of dimensions while keeping the same plunger volume and stroke length, both plunger and tube were cut about 20mm shorter. Note that this design lacks a shock buffer. I recommend using a thinner O-ring wrapped around the plunger teeth in a wavy pattern.
   

• (Optional) A tighter Conrod-Cammer-Trigger assembly
  All of these components were widened to provide 0,2mm (1/64") gaps, minimizing part misalignment while using thick (6mm, ¼") shock cords to fire.
   

• (Optional) A sightless Yoke
  The Yoke was shortened to allow the TopRail_max to be screwed on top of it.

Hardware

• All the hardware required for HYPR, except for the barrel tube.

• A shortened polycarbonate tube (35mm ID 38mm OD), cut to 82mm (3¼").

• 27x (total) of M3x10mm (4-40) countersunk screws.

• 6mm (¼") shock cord for plunger operation. May be changed to 8mm cord, but with 6mm single loop (both passes on the cammer) the pull is hard, much harder than on YEHW/YEHWSon

• 3mm or 4mm (1/8") shock cord for latch, extractor and trigger operation.

Known issues

• This design is still WIP.

• SYPR can't fire quad elite shells with no air distributor. Triple shells work OKAY, but sometimes they turn into inline magazines, shooting three half-darts with each shot.

• Ejector has no latch (like SillyPilot does) - the barrel has to be closed with a slam, otherwise the SillyShell rim can get stuck on the Base face seal.

• While running the blaster with ¼" shock cord, both Grips and Wunderbar tend to bend under load, leading to the whole mechanism misalignment and accidental discharges. I recommend printing the whole blaster with 5 perimeters, 20% infill.

• This design is prone to air leaks in Base plunger tube seal due to PC pipe stretching in roller-type polypipe cutter. I addressed it with thick silicone grease for plumbing rings.