A bit of a bulge yes. And my comments about a more "generous" chamber is probably more the leverage of the bolt pushing the rounds home than actual chamber dimensions, though the handloads with a bit too much crimp did chamber easily. The brass has a normal appearance. I have a revolver with minimal chambers - its a High Standard MkIII made for them by the young Dan Wesson company in 1973. It has recessed chambers and they are cut to minim dimensions. A lever action has not cylinder gap so I suspect that it produces a bit higher pressure than a revolver with the same loads.How does your brass look? If you were shooting full .357's, do they have bulges in the brass down by the base?
Just curious....