I've noticed the exact same thing on my 700's. Especially when the barrels are on the new side. I have run a pretty decent borescope down them and don't really see any inclusions or burring that would hang onto the copper more, but my eyes aren't what they once were.
I don't see how a design flaw could cause this. Hell, I thought it was just mine that did it.
I clean roughly every 500 or less as a preemptive action on those particular guns.
AR's get copper cleaned at somewhere between 3k and 5k though I can't say I've personally noticed any accuracy issues at those round counts. It's just a nervous tick and I just can't stand a nasty freaking weapon.

