Marushin M1 Garand Airsoft Gun Trigger Hammer, Updated 8/28/22

prusaprinters

<p>If your Marushin M1 Garand collector airsoft gun has snapped its hammer in half, then this replacement can get you up and running again. &nbsp;The hammer in the trigger assembly strikes against the gas valve knockers to start the blowback action and propel the BB. &nbsp;Over time, the repeated impacts on the hammer can cause failure in the cheap zinc alloy across the center where it is thinnest. &nbsp;Using green gas/propane pressure probably exasperates this condition. &nbsp;The only repair is replacement of the hammer, as epoxies and glues will not hold.</p><p>I printed this using Prusament PC Blend, as this hammer needs to withstand some serious punishment to actuate the gas valves without breaking. &nbsp;The PC blend is proving to be durable enough so far for HFC-152a (duster) gas. &nbsp;Green gas (propane) however does not work as well, depending on the temperature, as the gun will fail to cycle. &nbsp;My theory is the light plastic may not have enough mass to actuate the valves under green gas pressure.</p><p>Use either as many perimeters as possible to create toughness and prevent deformation at the valve impact sites, or use solid infill. &nbsp;Since this hammer needs to strike the valves knockers, it must be able to withstand sharp impact repeatedly, hence the solid infill. &nbsp;Remove supports in between the sear end and under the pivot pin groove. &nbsp;Be aware there is a supporting wall at the top that can be confused with support structures; don't rip out the supporting wall when removing supports! Using a .25 nozzle will enhance accuracy at the sears and may result in smoother operation. &nbsp;Both PETG and PC blend were tested, with PC blend being the best for its stiffness and toughness, albeit with some difficulty with warping. &nbsp;Use mouse ears or a brim, and turn off cooling to minimize warping with PC blend. &nbsp;Using poor filament or incapable printers may be unsafe in this application if the hammer sears were to fail.</p><p>This part is for the Marushin M1 Garand airsoft gun only. &nbsp;It functions as the original Marushin model intended, with the rear trigger sear catching the first hammer sear, then transferring to the second forward hammer sear after releasing the trigger. &nbsp;Failure of the sears can result in the Garand double-firing or not catching at all.</p><p>Dimensions have been tweaked over the OEM part to help prevent excess friction and minimize wear and tear. &nbsp;The stock hammer would rub unnecessarily against other sear surfaces, sometimes causing a jam. &nbsp;Using this hammer should help increase life of the trigger assembly as a whole by reducing unnecessary contact between parts, and being more forgiving to the cheap pot metal sear surfaces.</p><p>The second trigger spring housing part further improves reliability of the trigger operation. &nbsp;Sometimes the stock trigger spring housing would dip downwards when in the cocked position, which would jam the hammer from being released. &nbsp;This would prevent the airsoft gun from firing after a blowback cycle despite pulling the trigger. The improved part here has an extended arm that resists dipping downwards, and pushes the spring housing upwards. &nbsp;This maintains the proper geometry to ensure reliable spring force and actuation of the hammer upon a trigger pull.</p><p>A shim is also included to place on the right side of the hammer, opposite of the safety, to help reduce slop.</p>