A review of the Saami drawing of a 2-3/4" chamber (pg18)
The only way to get a true measurement is to make a plug at .798ø, drop it in and obtain the measurement. The plug end that's inserted into the chamber must have a dead sharp edge and the diameter (.798) is a basic dimension due to the fact all dims are at maximum material condition..meaning, no tolerance at all for the plug ø. The Saami spec was issued May 1979 & was revised July 2015 however it doesn't say what revision it is. (e.g., A,B,C, etc). There's also a note that clearly states "chamber lengths (per the standard) have been lengthened. Without a review of all revisions since 1979, that indicates the 'official' lengths increased in 2015. Therefore, since the PR's were made long before the revision...you have 3" chambers in a SCC despite the fact they're marked 2-3/4".
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Threaded Mode