Some Lefever information here
http://www.doublegunshop.com/forums/...&Number=466257
A 1898 Lefever G 12g was choked R .027" with a 3" length of constriction; L .036" with 4"
Daryl Hallquist has confirmed that an occasional Lefever 12 gauge has bores tapering from the breech to the muzzle (.756" to .708" left and to .715" right on one gun). Most have a standard U.S. .729" - .732" parallel bore.