I tried measuring the chamber length. I discovered that my 2 3/4 lenght shells are just a hair over 2 5/8 when fired, the 2 1/2 in. RST lites are a hair under 2 1/2 when fired; so I tried the rolled 3x5 card trick and it yield a suspicious 2 1/4 estimate. So will take it to a good L C Smith gunsmith near Wexford, Pa and have him go over the whole gun, especially preping it to avoid cracking the stock. Thanks for the help. Bill