Researcher makes a good case that Parker and Fox guns were intentionally short chambered - about 1/8" less than the shell they were intended for. So a gun chambered for 2-3/4" shells would be 2-5/8" and a 2-9/16 would be 2-7/16". I have a Philly A grade 16 and a Philly XE 16 with 2-3/8" chambers.

Here is one of Researcher's posts about chamber lengths: Link



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