At the time this gun was made, 2 7/8 inch, was the "standard" length for 10-gauge shells in North America. Longer shells, 3- and 3 1/4 inch were available at extra cost. Again, as has been stated many times about old time longer 12-gauge shells, these longer shells did not carry a heavier load, just more and better wadding. In my old shot shell catalogues, the heaviest smokeless 10-gauge loads were 3 3/4 dram equiv. and 1 1/4 ounces of shot. In black powder you could get up to 5 drams of powder with 1 1/4 ounces of shot. One and 1 1/8 ounce 10-gauge loads were common. All that being said about available factory loads, we know from reading that a goodly number of the oldsters were handloading their shells a lot heavier and hotter than the factories would.
Galazan has at least three different repro vintage Lefever butt plates --
http://www.csmcspecials.com/ProductDetails.asp?ProductCode=PB220
