Jeff;
I have not replied because I simply have no data on the bore size of 20ga Lefevers. One first has to have one to measure. I have measured several 12ga's, one 10ga & one 16ga. certainly not enough to establish a pattern. While I do not temember the exact diameter on any of them the 10ga is an early rod cocker & has oversize bores. An early 12ga two-hook gun likewise is oversize. Most of my large hook 12's as well as the post 1907 16ga all have bores close to standard. The early black powder 10 & 12 gauge guns were often bored oversize for use with the all brass shells & their oversize wads. I do not know if this situation applied to early 16 & 20 gauge guns or not. They were not near as popular for waterfowl as the larger gauges. In the 1890s as smokeless powders began to be used more & these were nearly always put up in paper hulls the bore sizes became smaller & much closer to the standard of 10-.775", 12-.729", 16-.662" & 20-.615". I highly suspect, but without having done a lot of measuring cannot verify that the vast majority of 16 & 20 gauge Lefevers were bored very close to standard. I thought someone who had actually measured a 20 gauge would chime in with more positive info.
