RE: breaking in a rifle?
A good, properly broken-in barrel will become lapped, smoothing over the bulk of the microscopic imperfections in the tube.
As a result, you'll have a cleaner barrel - one that doesn't get fouled-out as quickly, and it will be more consistent.
A box of shells costs what? $15-$40 depending on the rifle. If you can spend just a few dollars and ensure that your rifle will be as accurate and consistent as possible, why not?
Chances are, sighting in the rifle alone will take 6-12 shots, so while you're at the range, just take your cleaning supplies and run some solvent down the tube between shots, brush it out, and do it right. You have nothing to lose except a couple hours.
I break in every rifle I buy, and it pays off. Sure, it's a pain, but it's comforting to know that you went the extra mile while you had the chance.