My S&W 24-3 that I bought used was tightening up and jamming after
20 rounds or so. Based on feedback from the forum I bought a shim
assortment and pulled the cylinder and extractor rod and added .003” of
shims based on my measurement of b/c gap. So today I finally got to the range and fired 50 consecutive rounds without issue. I loaded and fired the cylinders without any breaks, and the revolver was noticeably heating up. But no tightness was felt even at the end of 50 rounds.

So thanks everybody for the advice when I asked a few months ago. The shims worked as advertised.

Willyboy