Trying to decide between a marlin cowboy rifle in 357 and 45 colt.Do either of the rifles have a leading problem?I prefer the 45 but have been hearing that because the marlin has a micro groove bbl it will lead the bbl.All my 45 colt loads are between 800 and 900 fps with a 250 lead bullet.Hope you cowboy shooters can help,there is a 45 cowboy in my favorite store right now for 490.