Marushin M1 Garand Part 45: Airsoft Gun Bolt, Improved 4/5/22

prusaprinters

<p>Note: Part is still being tweaked/optimized, but it's fully functional! &nbsp;Pictures may show an older version. &nbsp;Build updates below in the bulleted section. &nbsp;Obsolete models are deleted and replaced with the latest version. &nbsp;Post feedback so we can improve and keep these collector replicas running!</p><p>Change Notes</p><ul><li>4/5/22, Version 6: Best version yet. &nbsp;Dimensions tweaked for better fit. &nbsp;Diagnosed a sluggish and wasteful blowback system to an improperly engaging release pin. &nbsp;Pin releases the expanded gas inside the blowback chamber once the cycle has completed. &nbsp;A partially engaged pin will leak gases out of the chamber, consuming excess gas and slowing down the blowback. &nbsp;This bolt engages this pin further than the stock part between shots, preparing it for the next shot. &nbsp;See photos for details. &nbsp;Green highlights the improvement, and red shows the stock part.</li><li>3/27/22, Version 5: Dimensions tweaked again. &nbsp;Improved fit with hammer interface, air seal, and spring indent</li><li>2/15/22, Version 4: Through hole added per request. &nbsp;Mimics original design, but introduces potential for air leaks and may not hold up as well</li><li>1/31/22, Version 3: Durability testing revealed that the little retainer for the spring (sticks up off the main length of the body) broke off. &nbsp;I've significantly lengthened this section for more durability, after learning it's all empty space under the bolt cover.</li><li>1/24/22, Version 2: Refined port hole exit for better flow and seal against hop-up bucking. &nbsp;Noticeable BB velocity improvement.</li><li>1/24/22, Version 1: Refined charging handle fillets for better fit against receiver in resting position</li></ul><p>This replaces Part #45, a critical component of the Marushin M1 Garand gas blowback airsoft gun. &nbsp;Part 45 is the bolt, which often breaks where the handle attaches due to blowback stress, and unfortunately a spare is nearly impossible to obtain. &nbsp;This print will make your Marushin M1 Garand functional again. &nbsp;It also offers several improvements over the stock part, allowing for better fit and functionality. &nbsp;It should also reduce long term wear and tear on the rest of the zinc alloy parts this bolt interfaces with. &nbsp;Replacement is a direct swap-in with original Marushin parts. &nbsp;Lubrication with a quality grease like Super Lube on the sears, hammer, and bolt is still needed for optimal performance.</p><p>This part requires very strong, stiff, resilient filament, and a well tuned printer. &nbsp;I used Prusament PC Blend, which is performing perfectly. &nbsp;Polycarbonate blend has the right amount of impact absorbing flex for the blowback action, is stiff enough to activate the hammer sufficiently, 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. &nbsp;A 0.4 nozzle with .15 layer height and &gt;5 perimeters helps increase printing strength. &nbsp;A .4 nozzle provides better durability compared to a .25 after several test runs. &nbsp;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. &nbsp;A 3mf file with my brush on supports is included. &nbsp;A draft shield can help prevent warping; no brim is necessary. &nbsp;</p><p>Hole cleanup may be necessary. &nbsp;The holes are printed with a slight indentation on top to help print cleanly with FDM printing. &nbsp;After printing, remove any support structures remaining, and use a small file or sandpaper 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.</p><p>Note that frequent replacement may be necessary depending on firing conditions, quality of the print, and your filament choice. Long term durability is still under testing, and may undergo revisions based on results. &nbsp;Testing has been done with both HFC152a duster gas and propane/green gas, and so far this has held up to both types of propellant.</p>