I started shooting in 1963 and I have yet to "break in" a barrel. It was unheard of 15 years ago, now it's all the rage. I have yet to see any improvement come from it. Every time I go to the range there is always someone there scrubbing away with a cleaning rod. The whole thing is when we go to a break and go downrange to check our targets, their groups are never any smaller. Many times larger. I don't see any benefit. My guess is there have been far more barrels damaged by all of this cleaning and scrubbing, than have been improved. I'm noticing that I am seeing less and less of it as time goes by. I think the fad is wearing off. Bill T.