A barrel set that doesn't ring may be caused by the presence of the extractors, not lose ribs. Drop out the extractor(s) and they sometimes ring beautifully.
I agree that ringing barrels are rarely a sign that the ribs are 100% good.
The only sure way to check the ribs for bleeds/looseness is to drop them in a tank of boiling water and watch the strings of bubble appear.
Of the guns I have in for restoration, I doubt that 1 in 5 have perfect ribs but 4 out of 5 will ring just fine. Even fewer will be perfect after modern reproof and I now check ribs on arrival and after lapping and/or proof.
