ChristopherB,
I personally prefer a rimmed cartridge, but recognize that rimless extractors have been made for many years and are now very reliable. I agree with one of the above posts that it is one thing when you a facing an animal that is able and anxious to stomp you into a greasy spot, and quite another when you are hunting in your own backyard. Regarding "regulation", I have found that most of the problems come from improper bench procedures, and ammunition different than used to regulate the rifle( especially bullet weight). Both barrels must be fired as quickly as the sights/scope can be aligned and should be allowed to cool to ambient temperature after each pair of shots. Mounting a scope on a rifle regulated with open sights can also change bullet impact. The rifle should be held in both hands and the body should be upright so recoil will "rock you back" as if shooting "off hand".
Mike
