I am the only person I've ever heard of to have a dovetailed lump fail. I have a pair of 1921 Charles Hellis game guns that are "as good as" it gets. They have dovetailed lumps. The #2 gun failed on the 8th shot (2 1/2" 1 oz CIP shells) of being in my posesion - I had just shot four targets off skeet station #2. The issue was a "cold joint" in the braze of lump to barrels. There was only a tiny spot that had originally joined and you could clearly see the fracture's progress. The gun made a trip to Birmingham and is now in regular use.
The experience left no lingering doubts in my mind as to the utility of dovetailed lumps - they are fine by me. Chopper lumps may be considered the "standard" today, but there are many best guns that came OE with dovetailed lumps. If you are going to shoot older "best" guns, then you need to get past an hang-up that only chopper lumps will do. As of yet, we have no idea how long dovetailed barrels, damascus, and/or early fluid steel can be shot - it looks to be a very long time.
