The following is in reference to a 1985 Guns and Ammo article by the legendary Bob Milek. It can be reviewed here.
A couple points come to mind ref. the trigger job.
In the article he is stoning the long side of the striker holding it flat on a stone. He also is says to polish the front side (short angled tip) of the upper end of the striker. Not the best idea on either count. This produces a knife edge.
If you slightly round the tip of the striker, you will produce a greater contact area which makes for a smoother pull.
Also, since the striker's upper end on the one hand cams past the end of the trigger and on the other in some situations is jammed against the vertical surface of the trigger below the engagement or sear surface, a sharp edge is more prone to being bent, nicked, or otherwise damaged and no longer smooth.
Bottom line is that a sharp edge as produced by the methods Bob shows is not the best overall.
Also, by way of clarification, he says to polish the sear surface on the trigger.... top end that the striker engages. "Polish" means different things to different people. That surface is very, very short and polishing as it is usually thought of can ruin this surface.
Once the sear notch on the trigger is "polished" it will also then be very, very prone to disengaging or "bumping off" when the barrel is snapped shut. For this reason I undercut the surface, and what I always look for is a "resetting" of the striker when the trigger is pulled just part way, then backed off. I.e., the angled surface on the trigger lets the tip of the striker slide back under it and re-engage itself. Plus, the undercut of course helps resist bumpoff.
I use the fine cut 1/4" square Diamond EZE Lap to rough in everything and undercut the sear notch, then do the polishing with the 1/4" thick Wyoming stone. In both cases the stone or lap is held flat on the surface, then angled over to the vertical leg of the trigger. Vis., stand the trigger upside down with the top on the bench/table. The stone or lap is first held down flat on the sear surface, then the 1/4" thickness of the stone or lap tipped back firmly against the vertical part of the trigger. These two surfaces.... the sear surface itself and the vertical part of the trigger...... act as guides to help you 1) keep the surface level left to right and 2) cut the notch at the same angle.
Once you get the ground finish off the trigger's sear surface and get it under cut, it takes only a few strokes with the Wyoming Stone to bring it to a polished finish. With this slick finish, it is smooth all right, but also more prone to bumpoff, thus the need for undercutting.
It was good to see that he was using stones to do the work. Too many people whip out the Dremel, and this to me is a big mistake, especially when the EZE Laps and the Gunsmith size Wyoming Stone costs less money than the Dremel and does the work so, so much better.
Bob says to replace the trigger return spring, and this is great if you can find JUST the right diameter spring, which is always a problem. He cautions against shortening the return spring to reduce the pull weight in the event you get it too short. If you do, no biggy. Just stretch it back out a little.
Here is a somewhat coveted secret. For a really light pull weight, the external springs on tire valve cores are great. However, they are quite often too light to overcome the inertia of the heavy trigger when the barrel is snapped shut and thus bump off easily.
Tip. If you go for a light pull weight and have a problem with bumpoff, simply press your trigger finger against the side of the trigger and hold it forward while you snap the barrel shut.
Lest someone yell, "Unsafe," let me remind you the hammer is not cocked yet at this point. So long as the trigger is held forward so as to engage the striker ok, then the hammer can be cocked and life goes on normally. If it bumps off, as you know, the hammer will not cock.
Another tip. Much of the crunch and grind in the Contender trigger comes from the return spring and plunger in the easy open models. With the striker released, simply work the trigger and you will discover how much of the rough sensation comes just from this area, which can be aggravating getting rid of sometimes.
The old style triggers do not have this problem.
I get a little billious (not to be confused with any bill at the pond) sometimes when folks seem to think that tweaking the engagement screw to shorten the engagement constitutes something of a trigger job. There can be a lot of work that precedes this.
OK, moving on to another point that just came to mind. This is in regard to lowering the locking bolts to make sure they engage the frame far enough. Bob says to stone the bottom sides of the locking bolts. If only a very, very small amount of material is removed, this MAY be ok, BUT, by thinning the locking bolts top to bottom, they will then tilt more in the locking bolt slot in the lug, thus making them more prone to unlocking when fired. Take the material off the TOP side of the locking bolts, folks. Just use the Diamond EZE Lap or something similar that will keep the surface flat and maintain the established draft angle on the top surface.
Excuse the commercial plug, but I just got in a large shipment of EZE Laps. To me they are absolutely indispensable working on TCs... or jillions of other metal working tasks.