It seems to me that "barrel break-in" has only come about in the last 30 years or so, I used to subscribe to all the gun mags and I don't recall reading about it. Rifle testing by the writers usually involved checking the screws, making sure the action was snug in the stock and the rifle in a secure position in the rest. In 1979 I fired my NIB Winchester M-70 XTR for the first time, in fading light on a fall day I got a 1.5" group at 100 yards with GI ammo and iron sights, first time I fired my No. 1 SIG SHR, at 100 yards a 1.25" group with Remington ammo-and I am FAR from being an experienced CF rifle/long range shot. "Polishing" a rifle barrel is best done by shooting jacketed bullets. Just my $.02.