Being a little picky, but actually the replaceable "shoulders" are on the barrels, not the frame. True, they come on 682/687 from the factory, but these 682/687 barrels can be fit to a 686.
When I had a 687 "rebuilt" by Cole Gunsmithing, they welded and refit the barrel lug to the fore-iron and bushed the locking bolt recesses in the barrels. Thus, all the mods were done to the barrels; trunions and bolts weren't touched.
I put over 250k rounds through my first 687, only breaking a single firing pin. It's now tight as a virgin mouse and the new owner is still shooting clays with it. I own more expensive guns, but my comp gun is a 682.
