I spent my afternoon addressing the crap trigger today.
First step was stoning both sides of the sear and the hook. Especially on the sear there is nothing resembling a decent surface, it’s covered in paint and crudely machined. Flattening and polishing the hook was also important as probably 7-8 lbs of the trigger effort was overcoming the trigger springs (front and rear.) I decided to bend a bit of the tension out of these, but after you do that the very rough disconnector and hook surfaces will not disengage. I determined that even with a polished hook/disconnector you still need 3-4lbs to have the trigger reset reliably.
With the sear I also stoned the top to try and create a clean break point, not sure how much this helped.
I also lightly stoned anything else that looked like it was rubbing.
I also greased the disconnector hook and sear, not sure if this was a good idea or not but easily removed.
Finally, and the majority of the pull weight I think was the hammer spring. I think the gun’s trigger is grossly over sprung to overcome the crap machining of the trigger components. I bent quite a bit out of this spring to where I’m getting a 7-8lb pull overall.
All that’s left is to see if there’s still enough hammer power for reliable ignition. My feeling is that there is.
This was probably 2-3 hours of fiddling, I am not a gunsmith but have tools, some common sense, the internet, and had a milspec AR15 trigger for reference (the main part of the trigger works on the same principles, same pin spacing, but the hammer and trigger are wildly different, no easy drop ins.)
The thing that concerns me in the long term is the apparent lack of hardening or anything on the wear surfaces of the trigger. Not sure if this is a valid concern but I wonder how it will hold up.