Believe it or not but they smooth out fairly quickly through "normal" use - but I guess "normal" use may vary between individuals. When I bought my CZ in 375H&H mag brand new, I would put about 20 rounds through it each weekend while I was working out reloads for it. Initially the action was very rough and the magazine guide rails would score the brass but luckily I'm lazy and ended up not doing anything about it, and it came good by itself. Ultimately the brass was otherwise undamaged and lived a normal life to expire of the usual neck crack.
