In the case of chopper lumps half the lumps are a solid integral piece of metal with the each barrel. So called because the rough barrel has the outline of a chopper. (Cleaver or hatchet.) The lumps are machined out of the "blade" area. When the barrels are joined the two halves of the lumps mate together and you can see the vertical seam in the center.

In the case of dovetail lumps an area is cut out of the bottom of the barrels. The lumps are a seperate piece that slides into the slot in the two barrels. It is then soldered in place. The slot is so cut (in a dove tail) such that the steel takes the tensile stress while the solder is subjected only to compressive stress.

Can't say what shoe lumps are.