They, and other .410 break-open singles, are still fairly popular up here for ground-swatting partridge off the gravel roads. Constrictions are usually tight, and empty 3" #4 and #6 can be found on the roads. My 37 .410 has 0.020" constriction, more than any other nominally full .410 bbl I have.

A nicer, better scaled, Winchester .410 single is the Model 20.