my 1890 lefever pivot-lever 12ga has .749 -.750 bores...which appear to be original (and was told same by the seller - who had owned the gun since late 1970's). evidently, in the 1880's, quite a few 10's and 12's were bored and chambered for the use of (thin) brass shells...typically loaded with wads one gauge larger than the standard bore. at this time, i have not tried to "correctly" load my gun....but brass cases and circle fly wadding would seem to make it quite possible.

best regards,
tom

"it's a poor sort of memory that only works backwards."
lewis carroll, Alice in Wonderland