The late Mr McMillan gets quoted a lot on the lack of need for barrel break in (and not so much on the functionality of fluting) so I figure if I ever buy a McMillan barrel, I will not go through the shoot and wipe ritual.
Since both my other brand aftermarket barrel makers DID recommend break in, I followed instructions. It was a little tedious but at the end I had not only whatever smoothing was gained by firing single shots through a clean bore, I also had a hundred yard zero and chronograph readings to figure come ups for longer range. So the bullets and barrel life were not wasted, it was shooting I would have done anyhow, even with a McMillan.