I have a heavy-frame 682 acquired in 1989 and shot regularly since new. When I acquired this gun, all 682s were heavy frames. I think Beretta must have thought that the extra mass in the frame was important for their "competition" guns, but subequently decided that the standard frames are more than strong enough no matter how much they are shot. Now, as others have said, there is no difference in the outside frame dimensions between 682s and the others. My gun has had countless (well, I haven't counted) thousands of rounds through it and nothing has ever been replaced or repaired. About every five years, I pull the stock off and put fresh, dry lubricant on the internals. It's never dirty in there. No way for anything to get into the interior of the action except around the firing pins and it'd take about a century for that to matter. I am sure that I could say exactly the same thing if this were a standard-frame gun whether called a 682, 686, or 687. So I wouldn't worry about whether I was buying a 682 or a 686. Get the gun with the features you want in terms of barrel length, barrel venting, weight, and rib. If you end up with an auto safety, it can be converted either by you or a gunsmith to non-auto in about 15 minutes, most of which time is devoted to removing and replacing the recoil pad and stock.
