This isn't of much help for pistols but WWII battleship guns needed to be rebarreled after 200 rounds. The Italian high velocity 15 inch guns had to be rebarreled after 100. And that 1000 mm super gun that Gerald Bull (a Canadian, BTW) was designing for Sadam Hussein in Iraq would have had to be rebuilt after six shots. Of course it wasn't a weapon, it was a satellite launch system.