2 9/16" was never a standard chamber length in 12ga, it was the common length of a 16ga chamber in that era. 12ga Lefevers will be found with "Original" factory chambers in both 2 5/8" & 2 3/4" lengths, and other lengths to order. 2 3/4" shells were readily available by at least 1900, probably earlier, & this is a common chambering for Lefevers, particularly in the heavier weights (7¼lbs & over). The pins behind the fences are for the overhead sears to pivot on & also serve as firing pin retainers.
