On introduction in 1926 the chambers were 2 1/2"



"Soon thereafter" the standard was 3", but the shipping records the LCSCA received from BBHC in Cody did not include .410 chamber length, so we don't now how "soon thereafter".
The first 3" chamber .410 would be a nice addition to the L.C. Smith Chronology.
See "The L.C. Smith Production Records" by Dr. James Stubbendieck, p. 104

Brophy didn't say, and Houchins (p. 391) only has a Hunter Arms Engineering Specification chart from 1936 showing 3"

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