Model 21 barrels are of chopperlump construction. The lumps are then machined so they can be dovetailed together, then soldered rather than brazed which does not destroy the heat treatment of the barrels. This is a totally different system than British dovetailed barrels where the entire lunp is dovetailed to the barrels. I hope this makes sense.....it used to confuse me too.

Socialism is almost the worst.