Sear's Hobby Page

Lately I've been noticing an increase in the prices of ACM AEGs. Yes, in terms of quality they have improved compared to the time I bought my first JG about three years ago. Despite criticism on the quality of the material they use or the accuracy of the model, the use of these guns have grown to dominate the field. But now things are different. When I last logged on to the FAS forum, I was surprised to see ACMs with price tags that rivaled that of branded models from Taiwan and Japan.

It has been awhile since I built a gun from parts. So I decided to build one from parts I already have. My goal would be to build a replica of the Knight's Armament SR-16 with a 10-inch barrel for CQB. I had a spare version 2 gearbox (from my M4) to use so I took it out of my parts bin to see what could be used and what I would need to buy ( second hand to lower the cost). With the exception of an air seal nozzle and better wiring, my old gearbox remained intact.



Considering the fact that it hasn't seen use in more than a year, the internals looked pretty good. As I will be using an old spring, I was confident that the shell would be able to handle it.




The right side of the gearbox looked pretty good too. One can see the imperfections in the casting due the flashes and uneven color of the metal. If you scroll down a bit more, you'll see why the prices of ACM were so cheap back then.




Here are some close ups of gears and anti-reverse latch. For this picture I wanted to see what the parts looked like before taking them out to be cleaned. There is a lot of crud and old grease on the ARL, but no damage.




The trigger block looks well worn and may need replacement of the contact points or at least a good cleaning. Back when I was using an M4, two to three rounds bursts instead of prolonged fire was how I played in the field. Better to shoot and scoot rather than spray and become a target for another player with an equally heavy finger.


If your're wondering what that fiber on the trigger block is, it's hair from my ever-shedding dog. Overall, everything seems intact.


The tappet plate works in the sense that I could move forward and backward. The copper contact points show no outward signs of discoloration from exposure so I think they should be fine.





I took a shot of the sector gear with the gearbox closed to see if it would wobble when turned. As far as I can tell right now, there are no major problems that I should fix, at least internally. About the only problem I need to address would be the loosened threads at the bottom of the gearbox that is used to secure the pistol grip.



As you can see, the holes for the threads are much larger than they should be. Because of the quality of the metal, the threads easily loose their teeth from repeated opening and closing of the gearbox. I addressed the problem by drilling a bigger hole to accept a thicker screw.




If you look at the hole on the upper left, that is how the thread originally looks. A part of the original screw broke off so I would need to drill it out and then make a new thread. The hole on the lower right had been worked on and is using a much larger screw. So far, it works but I need a long term solution for this. Another thing you may notice is that the seam lines running through the thread holes. Based on this photo, it appears that each side of the shell was not casted as one piece but two. Whether this had something to do with the loosening of the threads I can't say now.




This is outside of the right side of the gearbox. These lumps may have been caused by oxidation from neglect and I would need to sand off the paint to see what really happened.

So that's it for now. I have a working gearbox that needs some repairs so I don't have to worry about the pistol grip coming off during a game and I need to see what lies beneath the paint in order to assess the real state of the gearbox.