I have a German single shot 16 ga on the Lefaucheux action. I had a gunsmith epoxy a Gaugemate 16:28 ga adapter into the chamber, cut a notch in the rim, put a grubscrew into the extractor, bingo, a 28 ga SS which earns its keep as a ruffled grouse and squirrel gun around the farmyard. I load 28 ga shells for my Remington 11-48, a cute gun if there ever was one, so I have lots of 28 ga shells around.
Gas obduration is complete looking at the spent wads. I know they should not work but they do, as do my little skeeters in 12:20 ga.
Mike