First let me say David that I enjoy your posts (comment in reference to a previous poster comment). No, I would say that Dave T's gauge wasn't specifically for LC Smith's as he is an english gun guy primarily but he was very emphatic in his measurement and watching how carefully and correctly he does everything I'm sure he did it right and with the right fauge for the job. It was an experience just to watch him disassemble and assemble my 12. You'd be hard pressed to tell if any of screws ever had a screwdriver touch them. Back to the chamber length. Whatever the bore diameter is I'd say it's touch to see much change in 1/4" with a 14 degree taper. But I'm not a machinist.