Marushin M1 Garand Airsoft Gun Part 45 Bolt

thingiverse

Note: Part is being tweaked/optimized, but it's fully functional! Build updates below in the bulleted section. Change Notes 1/31/22, Version 4: Durability testing revealed that the little retainer for the spring (sticks up off the main length of the body) broke off. I've significantly lengthened this section for more durability, after learning it's all empty space under the bolt cover. 1/24/22, Version 3: Refined port hole exit for better flow and seal against hop-up bucking. Noticeable BB velocity improvement. 1/24/22, Version 1: Refined charging handle fillets for better fit against receiver in resting position This replaces Part #45, a critical component of the Marushin M1 Garand gas blowback airsoft gun. Part 45 is the bolt, which often breaks where the handle attaches from related blowback stress, and unfortunately a spare is nearly impossible to obtain. This print will make the Marushin M1 Garand functional again. It should also reduce wear and tear on the rest of the components, as the printed plastic is softer than the zinc alloy it interfaces with. Replacement is a direct swap-in with original Marushin parts, no additional parts necessary. Lubrication with a quality grease like Super Lube is still necessary. This part requires very strong, stiff, resilient filament. I used Prusament PC Blend, which is performing perfectly. Polycarbonate blend has the right amount of impact absorbing flex for the blowback action, is stiff enough to activate the hammer, and prints easily enough in case multiple replacements are needed. Other filaments may work, but this part experiences tremendous abuse under firing conditions, and needs to be tough as possible. A 0.4 nozzle with .15 layer height and >5 perimeters helps increase printing strength. Print with supports under the bottom of the bolt, under the rear circular guide, under the front gas exit port, and optionally in the side gas port entry. A 3mf file with my brush on supports is included. A draft shield will help prevent warping; no brim is necessary. Hole cleanup may be necessary. The holes are printed with a slight indentation on top to help print cleanly. After printing, remove any support structures remaining, and use a small file to smooth the flat undersides of the bolt, round out the bottom rear edge where it interfaces the hammer, and slightly round the edge of the right sear where it interfaces the blueback valve knocker rod and arm in the receiver Note that frequent replacement may be necessary depending on firing conditions and your filament choice. Long term durability is still under testing, and may undergo revisions based on testing. Testing has been done with both HFC152a and propane/green gas, and so far this has held up to both types of propellant.