I disagree thereYa know, cleaning your rifle good between strings is like showerin' between workouts. Doubtful it makes us better athletes, but it sure can't hurt any.
Geno
The best barrel manufacturers in the world recommend a break-in of some extent.
http://www.shilen.com/faq.html#question10How should I break-in my new Shilen barrel?
Break-in procedures are as diverse as cleaning techniques. Shilen, Inc. introduced a break-in procedure mostly because customers seemed to think that we should have one. By and large, we don't think breaking-in a new barrel is a big deal.
I'm "against" break in. If your rifle has "tooling" marks and "pits" the copper from your bullets will fill them in and essentially smooth out the bore.