Most premium barrel manufacturers consider a barrel to broken in at 100 rounds. The usual deal is to clean it every shot for the first 10, then every 5 shots for the next 40 - then shoot it as normal after that. I have seen the group size, with the same load,shrink in half from the first group fired (shots 11 through 15) to the group shot at 100 rounds. Some bench rest shooters say that they fully "settle in" at around the 200 round point - they are dealing with a few thousands of an inch better, though.