Only two totally reliable means of measuring length I know of are the system that Jim Legg describes above and a proper (bore micrometer) bore gauge with ruler. When using the system Jim Legg describes, I also use a good light to verify that the end of ruler is actually stopping at start of forcing cone. After finding that some of my old European hammer doubles have chambers that standard American chamber gauges show as 60 or less mm, I ONLY trust these two methods of measuring chamber lengths.
Niklas
