NiklasP,
Since the chamber is the diamiter required to fit the shell exterior it seems the forcing cones restriction would be minimal. It would seem the forcing cones assists with the development of pressure depending on the wad sealing abilities. The cones don't force the shot cup to a smaller diamiter as is done at the choke. I belive this to be true but sure wish Mike Orlen would come back with some technical help. I have only laymans logic. I haven't seen any bulged barrels at the chamber end but that sure doesn't mean it never happens.
Best,
Ron
