I was searching for info on a Walter Cain lock I bought yesterday and found this thread. I also got a single set triggers in the deal.
I have to take sides with those wo do not consider single set triggers safe. To set the trigger before going to full cock is not a good idea, ..IMHO. I bought a single set trigger a while back and decided to not use it because of my safety concerns
Aside from the wrong order of operation to fire the gun, the pull is way to light. The set trigger set screw only changes the sear engagement depth (creep).
I bought an Italian target pistol that works the same way. The pull weight is fixed at near nothing. That invites the AD because the trigger can be tripped when the hammer reaches full cock. IT is that light. On my first outing to the range I had and AD with that pistol. I am a bit afraid of that pistol.
Back to the Cain lock. It had a hex head grub screw though the plate that was as originally made. IT bore on the sear tail and allowed for reducing the sear nose engagement in the tumbler notch from the outside. Sears and notches need proper depth of engagement and geometry for safety, and durability. If properly made there is no reason to have an adjustment for sear engagement. I plugged the hole in the plate.