MK23 Shell Adapter [STL]

MK23 Shell Adapter — tough, reliable, SLA-only

Made from scratch and tested on my Novritsch SSX303. Uses the original gas route and lips from the stock mags, but fixes the stuff that annoyed me in other DIYs.

Why it’s better

• Proper BB retention — only 1–2 BBs drop on reload, not a handful.
• Hose clamp to stop the Festo connector twisting and stripping threads.
• Strong ejection pin (option to add a second loose spring for extra kick).
• Swappable shell latches (2.4 / 2.6 / 2.8 / 3.0 mm) so you can fit different shell heights — minimal sanding may be needed.

Important — what you need

• SLA printer required (no FDM workaround).
• You’ll need common hand tools and parts (listed below). A full build guide will come later; the parts mostly make sense where they go.

Parts list

• 1 × M2 × 8 mm (shell opener)
• 1 × M2 × 5 mm (hose clamp)
• 1 × M2.5 × 16 mm (latch)
• 1 × Rod 2 × 18 mm (BB retention)
• 2 × Ø4.5 mm springs (15–20 mm)
• 1 × Festo QSM-M7-6-I (hose connector) + ~10 cm 6×4 mm hose
• 1 × HPA connector (US or EU style)

Printing notes (tested)

• Print on SLA (I used Anycubic Photon M3 + Anycubic flexible tough resin).
• Print angled with supports. Manually remove any supports inside the mag interfaces (threads, BB route, internal gas chamber) — these must be clean.
• Exposure/settings: I ran ~5 s exposure on the Photon M3 (adjust for your resin/printer).
• Post-cure and test-fit before final assembly.

Field tip
If the Festo connector has any play, add the hose clamp and a drop of threadlocker on the small threads for long game use.

License
You may 3D print this model for personal use and share photos of your prints online. You may not use it commercially, modify or adapt it, or share, sell, donate, or exchange the digital files or printed models. Please respect this.

Questions or build shots — hit me on Discord: https://discord.com/invite/XFdMX947JP

Digital delivery: After your payment is confirmed, your file will be delivered automatically. This usually takes 2–5 minutes. You’ll then receive an email with a download link