I like cheap ones like coreloks. Sometimes barrel breakin works, most of the time not. Its really a tool to get down to some serious load development. Anybody that shoots long range will see a new gun, have large velocity std. dev. the first 100 rounds or so. that should settle out. Following breakin procedures can lower that down to 20 rounds.

Breakin procedures are not what is wrote out there but to observe what is happening and make adjustments based off of that. If you see no copper fouling after two shots, then try 5. Keep cleaning and shooting until you see little to no fouling at 5. Try 10. But most likely what will happen is, youwill see copper fouling after each shot for 5 or so shots, and then you will see copper fouling after 3, and you can never get better than that.