I did the adjustable sear.........................
and it was a BEAR, because I'd never done one before. If you haven't, I'd suggest getting a few of those balls from CZ/USA, as they can go zinging across the shop veeeeewy easawbwy, never to be found, until you are finished and the rifle is gone.
Another thing I found handy, and I know there are better things, but, this is what I had handy.
It is recommended that one "lubricate" the ball & spring w/Vaseline, to keep the ball from departing when you lose it. (reduction of SPROING-Y ness
) I have found a small bladed screwdriver to push the ball & spring into the detent hole, but I lubed it w/"Bag-Balm". Its thicker, and actually kept the ball from going more than about 6-8" after slipping by.
There is another pin you use on the sear, and you may have to polish the holes it goes through on the rifle to get a good fit. And I did find their pointed pin(to get you in the holes faster), needed to be polished down in the drillpress w/some paper. But it all turned out to a first-class job. Its just that when you start, you'll think you need the hands of a Thai Goddess..............but don't give up, its possible, and I found the initial frustration was minimal after I got it in and adjusted.
Now that I have at least one done, I wouldn't hesitate to do another, the adjustment to the sear can give a spectacular let-off. It appears very well done, limits the engagement, a fine job, really. The guy that owned the rifle likes it very well. HTH