I have a CM.700 airsoft sniper rifle replica that started slam-firing[1] recently, likely due to a stripped sear. Is there anything that I could do about this, short of buying a specialised trigger box that costs as much as the gun itself?
I was thinking about making my own sear, but I took the trigger box apart in order to see what part could be the sear, and frankly I’ve still got no clue to this day. Despite taking apart quite a few airsoft guns before, this trigger mechanism is still a mystery to me.
I’m currently away so these images (1) (2) (3) are the best ones I have. The first one is the inside of the trigger box, sans the bar used to connect it to the bolt and outer barrel (it is positioned in between the two bars sticking out of the top of the box). The second image is of the bolt itself and the third image is of the assembled trigger box, showing three bars coming out of it (+ safety lever partially obscured by the bolt handle), and the outer barrel with the bolt inside. The bars sticking out of the trigger box slot into the holes in the outer barrel.
If it is the sear that’s being the problem here, would it be possible to somehow mold it back into shape, or would I have to make an entirely new one? Again, I could buy an upgraded trigger box, but my financial situation currently prohibits that, so having a cheap fix would be really nice, even if it would be temporary.
I would greatly appreciate any help.
[1] - The CM.700 is a sniper rifle with a rotating bolt action. The bolt is rotated up, then pulled back. At the apex of the pull, the sear locks, making an audible click. Then the bolt is pushed forwards, chambering a BB, then rotated downwards to lock it and make the gun ready to fire. Slam-firing happens when the sear does not lock back at the end of the pull - releasing the bolt will make it slam back shut. Sometimes the bolt will stay in the pulled-back position, but even a slight disturbance will make it slam again. (Video on reddit showcasing the issue)
Insofar as I can determine, a parts diagram from one of the myriad of models your gun is cloned from, or vise-versa, is available in this manual here. Here’s the relevant excerpt if you don’t want to load a .pdf:
Alas, the part numbers on that diagram don’t seem to go anywhere. Allegedly the sear from the Tokyo Marui L96 fits these, including the various aftermarket upgrade options for the same. The actual sear is in position 08-3 in the lowermost assembly on that diagram, dead center along the top right edge.
It is unlikely you will be able to reshape or grind the sear such that it works correctly again. The problem will undoubtedly be that the surface on it that matters has been worn away. It’s similarly unlikely you’ll be able to add any material back to it. It’s also probably cast out of potmetal, so it’s not like you could weld on it or anything. You can get a new steel aftermarket upgrade sear for around $30 online, which is probably the simplest option.
Manufacturing your own for this would be a fraught undertaking for somebody who didn’t already have the equipment and experience. I’m sure it’s possible, but don’t hold your breath on results if it’s your first time making a precision mechanical component from scratch. However, if you have access to a 3D printer it should be reasonably simple to print a very temporary replacement (printed plastics are unlikely to last more than a couple of shots) to verify that the sear was indeed the problem.
But it probably is.
Thank you so much! Weirdly enough (and the parts diagram you sent confirms this), my rifle seems to be running some completely different trigger system to the ones I see everywhere on the web, so I think the best choice will really be to just get a replacement trigger box. It’ll make any future replacements that much easier too, since it will actually be possible to buy compatible sears. Thank you for the 3D printer idea! I do have a friend who has one, so I’ll model and print a new sear to try and see if it’s the sear causing all this.