exact diameter should produce better accuracy,that was the norm for the dual cylinder rimfires. .001 difference will not exactly "rattle" and did not as a rule produce excessive leading, this could vary from barrel to barrel. my colt new frontier never had a problem and it fact i still have it. i got rid of the ruger simply out of preference for the colt, do not shoot a 22 pistol enough to justify,for me, the colt and a k-22 s&w are enough in rimfire revolvers. i do like the ruger centerfire in both single and double, but that strays from this thread. i am not meaning to put down anyone's thoughts, just trying to set forth the facts i have learned.