The A5s had a bit of notoriety for ring bulges well before the days of steel, Larry. The tightly choked guns that were fed a steady diet of bigger pellets of lead shot often had bulged barrels.
I've never seen a rib pop on a bulged gun. That doesn't mean it couldn't happen. One of the regulars here (Don Moody?) astutely pointed out a few years past that pressure would be reduced as the load came to the bulge. Ahlman's Custom Gun has been saying the same thing as Browning for years, it is a cosmetic issue when the bulge is at the muzzle.
It would bug me if a good double had a bulge, however.
Best,
Ted
