In working on my lock, I've done all the things Lewis describes in his great post on single trigger TC work (https://www.modernmuzzleloader.com/threads/tc-single-trigger-“trigger-job”.31395/). I've also changed the angle of the sear engagement surface on the tumbler to the flat surface on the tumbler adjacent to it from about 90 degrees when I started to about 85 degrees now. Lewis carefully avoided any change to the sear engagement surface of the tumbler. I had to change that angle to increase my trigger pull, which was probably less than a pound (I didn't have my trigger pull scale yet) when I started to work on it. In addition, I've carefully identified all surfaces in the lock that move in contact with other surfaces, and polished them up as well as I can with 600 grit abrasive paper. The polishing effort provided big dividends in that lock operation now has much less internal friction, resulting in a much harder hammer strike and faster lock time, even though it had little effect on creep or trigger pull weight.
A couple of things that Lewis doesn't discuss in detail in his great post on TC trigger work are that: 1) As you file down the tip of the full cock notch, you have to make sure that the surface you're removing material from stays flat, and maintains the same angle to the rest of the tumbler, because if you don't do that, the trigger break will become mushy and lock time will increase (see below); and 2) You will reduce creep as soon as you start removing material from the tip of the full cock notch, but you won't start to reduce trigger pull until you start reducing the area of contact between the sear and the sear engagement surface of the full cock notch. The area of contact isn't big to begin with, so it's necessary to proceed VERY slowly to avoid removing too much material and ruining your tumbler. Lewis admits that he actually ruined the first tumbler he worked on by removing too much material. Lewis' approach to reducing the trigger pull does concern me a bit because it seems to me that the trigger has to become unstable if the area of contact between sear and trumbler becomes too small. However, Lewis and several others report that even when they reduced their trigger pulls from 12 lbs to 2 lbs, the trigger was still stable, and passed the "bump test."
Because I am trying to INCREASE my trigger pull, I followed Lewis' procedure only to the point that most of the original horrendous creep was gone.
Changing the trigger pull by changing the angle of the engagement surface on the tumbler is very tricky, because you have to ensure that: 1) The sear engagement surface of the tumbler stays parallel to the sear; 2) all flat surfaces stay flat (it's very easy to round them as you remove material with a file or abrasives on a sanding block); and 3) the edge of the full cock notch stays parallel to the sear - same concern as in 1) in the paragraph above. The latter (Point 3) is essential because if the sear engagement surface is not parallel to the edge of the full cock notch, when the trigger releases, the sear will drag across the edge rather than cleanly disengaging, resulting in a slow, mushy feeling trigger break. When I realized all these things and finally got it right - through a long process of small, incremental changes made by dry firing many times after each change, carefully observing the resulting wear marks on the surfaces, and then removing more material accordingly - my trigger pull was suddenly crisp and completely free of creep. At 2 lbs and about 12 ounces it's still a little lighter than I would like for a hunting trigger - but it's so free of creep and so nice and crisp that I'm pausing my efforts until the tumbler and sear contact surfaces have had a chance to wear each other a bit and stabilize. I've been dry firing about 50 times a day, and so far progress is in the right direction - the trigger is becoming even crisper and slightly heavier as the surfaces wear.
Coming up I hope to find the time to take some photos, identify the different parts of the lock and the surfaces and angles I modified, describe the tools I made to work on it, other tools that I used, how I used all the tools, and so forth. My goal in doing so is to document what I've done so that others who are considering doing some trigger work can have the benefit of my experience and what I've learned.
