General up keep as per usual stuff that we do post shooting will negate the rust developing as you said putting 10-15K rounds through it there will be a few more scuffs not just on the barrel as inevitably things happen.
I would not mind any of my barrels doing 10-15,000 rounds the only one I have heard being able to do that round count is the barrel they fitted to the E4 - M60 which they claimed was good for 15,000 before changing.