To do this mod you will need 1 SL-68 trigger spring, emmery cloth or automotive sandpaper 220 grit, 320,400,and 600. And if you will be doing the bolt work a dremmel tool with assorted grinding bits and a fine stone is also helpful.1. First step is to polish you're trigger and sear, here you want to polish the metal to a glassy smooth finish. Polish all sides, and pay close attention to the contact surfaces of the trigger and sear. Start with the 220 and move to the finer grits. Be careful not to remove too much material, all you want to do is polish, and reduce friction here.
2. Next is the rear bolt (hammer). The best way to polish this part is to fit a wooden dowel tightly into the rear of the bolt then insert the dowel in the chuck of an electric drill. This will cut down the time tremendously. With the drill on medium speed, and the o-ring removed start polishing. A good way is to place the drill in a vise and lock the trigger on for hands free operation. Again start with the 220 gr and work your way up to the 600 gr. Polish the bolt until all those nasty factory ridges are gone and the bolt is as glass. (Be especially careful around the front edge where the o-ring sits, go light here)
3. Now for the finishing touches on the bolt. Here you want to grind down the ledge of the bolt where the sear hangs up. This will cut down the trigger travel required to release the sear. Grind it down, and leave about 3/32" of the ledge. Any less than this and you're safety will turn into a selector switch, allowing the gun to fire full auto when the gun is on safety, and semi when it is off. Not tourney legal but this is how my gun is set up (1/16:" left on ledge for that function) extra care should be exercised when handling the gun here, due to the fact that their is no safety. With the grinding done use a fine stone to polish the ledge, remove all grinding marks and make it is perfectly flat and smooth, be sure the corner is sharp.
4. Now for the rear of the bolt, there is a cup shaped recess there to guide the sear as the bolt travels back. Here you will need to use a conical bit to lengthen this groove and break the edge a bit. Periodically this area will need some touch up. Polish with a conical polishing bit. Again mirror smooth.
*. Another thing I like to do which is optional is to grind the sides of the trigger where you're finger goes. This is just to take that square fat stock feel out. Here I round the sides and smooth them out, then polish them. This feel is very nice compared to stock. Just a nice custom touch.
* Another option is to install a set screw in the trigger to stop the overtravel after the sear lets go of the bolt. Since I took the ledge down to 1/16" on mine the stop is the safety. With the safety on, the trigger only travels a little over 1/16" before it fires. You can thread a set screw into the trigger where the swirl of your fingertip is placed to shoot. Mark this spot, drill it and then tap to accept the screw. When the final adjustment is found here, mark it and then remove it, add lok-tite and reinstall. That is all the polishing and modifying, now the re assembly/install the sl-68 spring in place of your stock trigger spring, leave the stock sear spring. Another trick to take the play out of the trigger assembly is to install thin plastic washers on both sides of the trigger and sear to remove any side to side play. These are easily made from any thin stiff plastic you can find; I used transparency sheets like your 6th grade teacher uses.
