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Last night, during an airsoft indoor CQB, my beloved APS ASR106 Mini Patriot M4 pistol rifle failed. Its trigger stuck in the safe position even though I rotated the mode switch to semi-auto and full-auto. After getting home, I took apart the gun and found the failure to be inside the version 2 gearbox. Disassembling the gearbox, I found that the trigger post had broken off.
Examining the trigger mechanism, I realized that the trigger post is molded as part of the gearbox. It prevents the trigger contact switch from traveling too far back. In semi-auto mode, when the sector gear moves to a certain position, it trips the semi-auto level arm, which lifts the contact switch off the trigger and snaps back to the trigger post. Repeated hits on trigger post in this manner causes the pot metal to break. And the gearbox is not an inexpensive part to replace.
Why they don't make this stop on the trigger mechanism itself is beyond me. After learning about this problem, I start to think up solutions for this common problem. In this article, I will detail out each solutions so that you can find the proper solution for you gun. I don't know whether other AEG gearbox versions have this same problem. Maybe you can chime in and let us know.
Replacing the entire gearbox or the gearbox shell is probably the most obvious and the most straight forward solution. However, it is definitely not the most inexpensive solution. At the time of this writing, APS gearbox shell costs $40, while the entire replacement gearbox costs $78.
Replacing the entire gearbox is the most expensive method, but it is the easiest, because you don't have to take the gearbox apart at all. However, if you go the gearbox shell method, then you will have to do a bit of work transferring parts.
Replacing the gearbox is certainly cheaper than buying a new airsoft gun. But if you are looking for even cheaper solutions, then read the next few sections below.