I just put one back together for someone that took it apart. My suggestion is don't take it apart.
The lower receiver , if you will, is Zamak, and the pins are the kind with the fins that displace material when they are put in. This means you only get to insert the pins (you'll need a hammer) a few times before the holes are wallowed out.
The way the disconnector works is tricky, and its a method I haven't seen before.
There is a steel channel that holds the trigger and the trigger spring. The channel has two pin holes going though its sides, and two rectangular cutouts in the bottom. In the gun, the bottom of the channel faces up (does this make sense?) One of these cutouts is the sear, and the trigger passes through the other. The trigger has two holes. The pin that holds the lower rec., channel and trigger together goes through the lower hole in the trigger.
The upper hole in the trigger is used used to retain a letter A shaped piece. This piece acts as both the disconnector, and the means to push the channel down, to release the hammer. The thicker part of the disconnector goes to the front of the gun. The disconnector rotates fore and aft relative to the trigger.
There is another pin hole between the sear and the trigger pivot hole. This hole is the pin that holds the trigger spring. As far as I could tell, both legs of this torsion spring point to the rear of the receiver. This spring is used to load the sear, and to reset the disconnector.
When the trigger is pulled, the disconnecotr pushes down on the channel, pushing the sear away from the hammer. the hammer falls, the gun fires, and the bolt comes back, driving the hammer down. The hammer strikes the disconnector, pivoting it, so that it passes through the trigger cutout in the channel. This allows the channel to pivot up and catch the hammer hook. When the trigger is released, that "A" pops back though the hole and resets the trigger.
Your best bet to improve the trigger is to weld up the hammer hook to decrease the sear engagement, which must be almost 3/8". However, if you really want a semi-auto .22 with a nice trigger, I'd look into buying a different gun. I highly recommend not disassembling this gun. Please do not disregard my advice. I work on guns for a living. The major pins displace material in the receiver. The minor pins are so loose, that I had to use grease to hold them in place while ressembling the gun. I had to make a tool to hold the parts in place, to push against the springs, to get the major pins in place, and even then it still resembled a monkey fornicating with a football.
