I have read that, for best guns made during the damascus barrel era, chopper lumps would not have been possible, because damascus is insufficiently hard to resist wear on the bites and hook. (And also because the lumps couldn't be fabricated by winding the barrels around a mandrel?) How were damascus barrels fastened to the lumps? Brazing? Dovetail?
Most were probably dovetail. Ask CrossedChisels about chopper lump damascus. Sometime back he mentioned having worked on a gun (Purdey I think) that had them.
Was there a transition period during which some best guns still used dovetail lumps and others chopper lumps?
Not sure that there's any firm date. By observation though, best guns with dovetail lump barrels don't seem to have been particularly unusual up through WWI.
I have also read that chopper lump barrels are themselves a compromise, because the steel characteristics that are ideal for the barrel tubes are different than the steel characteristics that would be ideal for the lumps, in that the barrel steel needs to be more resilient, while the lumps should be harder.
True, at least in theory.
The British auction report in the latest DGJ mentions that Boss has rebarrelled some of its guns using dovetail lumps.
Some were originally built with dovetail lumps.
While this would save the need to fabricate and fit the lump area, it would require cutting and fitting the dovetail. I wonder how much labor is saved?
The cost savings is in the blank, not the labor, chopper-lump blanks being more expensive.
It appears that some older best guns could have original dovetail lump barrels.
Champlin's has a Holland Royal Ejector on their site now, built 1912, with original 20 bore Paradox dovetail lump barrels.