Chamber length Win. 21

[jeffery c]

I measured a first year Win 21 12 gauge at 2 5/8". My 1948 LC Smith measures 2 3/4". My 1948 Ithaca is also 2 3/4". These are all unmodified guns, in my opinion, based on examination. I was surprised the 21 has the shorter chambers.

I have reviewed a lot of posts on this subject and it seems clear the consensus is that chambers cut to to 2 5/8" were intended for notional or unfurled 2 3/4" shells, as 2 3/4" shells measure about 2 1/4" before firing, maybe 1/10" longer. Do roll crimp shells vs star crimp shells affect this thought? Do roll crimp shells measure different than star crimp shells before/after firing? What was in common use in the 1930s? I have the idea star crimp plastic shells came about later. When did the makers begin cutting chambers to 2 3/4" as a routine practice? What are everyone's thoughts here?