hoppdoc,
Look at it like this. There is wear on both the bullet and the barrel. If you could fire a thousand shots, using the same bullet and a new barrel for every shot, you would have a very sorry looking bullet and a heap of pristine barrels. It is a matter of repetitive use and the lower one can hold the temperature and the pressure, the better. With doubles, there is the additional factor of the expansion of the barrel that accompanies the bullet, some more than others. With bolt rifles, it is of lesser consequence. At worst the rifle can throw the sights. With doubles, the assembly is more intricate and fragile.

As for wear of one metal on the other: In the manufacturing process most bullet manufacturers use carbide tooling that is much harder than barrel steel. Tooling wears out and that is under conditions optimised for tool life, with copious lubrication and heat control. There is precious little of that for the trip the bullet takes down the bore.

We are leaving for the Aim Show in Johannesburg shortly. Back on Tuesday.