Sometimes it takes a gunsmith more than one try.
I have guns I run “old” ammunition in. Most of my “good” doubles (all of them, to me, actually) get fed better, more current stuff.
Your gun features French single proof, fairly stout, but, I’d wager the right one that the Federal load you fed it, is outside the pressure the gun was expected to be used with, day in and day out. The rim separation is more than a bit concerning to me, and, I’d stop using that load in your gun, posthaste. Did the opened shell have a rough, or, torn appearance, up at the business end, after it was fired? Classic symptom of a hot load, fired in a short chamber, or, a steep or stepped forcing cone. The rim separation might indicate a chamber that has suffered a polish that was too great, or, inconsistent.
That should be a good little gun. That design is common as the rain France and Belgium, and I probably handled a hundred of them over the years I was importing French guns. It can be put right, in that I have no doubt.
Best,
Ted
