I can't remember if this is the thread that is appropriate, but this post is pertinent to the question. Below is a photo of my Late Ketland (Chambers') lock in my Kuntz rifle. So far I've purchased three frizzen springs for the lock hoping to eliminate frizzen bounce back, but without success. So, I ground a little off the bottom of the frizzen's stop to allow it to rotate a little further, but it didn't seem to have any effect. Still, flints were being sheared off by about 1/8", and though they still worked, their life was radically shortened.
So, I thought perhaps a little more pressure (stronger spring) would help, and re-arced a frizzen spring. Then, while returning the roller, I broke out the back support arm. $#@*!! While doing this job, the spring arm needs to be well supported over a plate with a clearance hole for the pin...word to the wise!! I installed a factory spring, and since I'd taken a little off the stop, it rotated a little further and the spring had no tension against the frizzen's toe at rest position. Two choices now - spread the spring a little, or replace the wheel/roller. I made a new roller out of 5/16" drill rod. The old roller is .250" with a 1/16" bearing hole. The new roller is .3125" and though it fits nicely, it will not allow the frizzen's toe to pass since the wheel is too large and strikes the spring's boss. So I slowly ground metal off the roller until it would allow the frizzen to close and open, and ended up with .297" diameter. It allows the frizzen to open and close, and completely eliminated the bounce back issue. Eueka!!