Bruce has previously made the point that some factory 20g cases are shorter than 2 3/4"
Estate (Federal) 2 5/8"; Fiocchi 2 11/16"; Nobel Sport 2 3/4"; Winchester 2 5/8"; Winchester Universal 2 9/16"; Remington Gun Club 2 11/16"
If the case mouth looks like the one on left,
it's a problem in YOUR gun
A summary of “Long Shells in Short Chambers”, by Sherman Bell with technical assistance from Tom Armbrust in “Finding Out for Myself” Part V,
Double Gun Journal, Winter 2001 is about 1/3 way down here. This was a PRESSURE, not RECOIL study
https://docs.google.com/document/d/1...vwLYc-kGA/edit