Rohann - Breaking in a barrel involves shoot a round and clean, repeat, shoot a few rounds and clean, repeat, shoot a few more rounds and clean, repeat. It is reported that after doing this for the first few dozen rounds the bore will copper foul less, and clean more easily. Some custom barrel makers support the practice, others don't. There are those who believe that break in is more important with a factory barrel than with a custom. As far as break in procedures go, it won't make any difference if you use decent surplus, or white box commercial. If you shoot standard 147gr. milspec ball ammunition, the only thing you will notice is that accuracy will be less than with premium target grade ammunition. Commercial target grade ammunition isn't cheap; equivalent handloads will be just over half the price.