Well this is an interesting conversation, many good points and mis information, .22lr is .222, .22mag is .224", so the mag is not loose in the bore but tight, and not much ammo to choose from, many find one or the other works the best, especially in the model 63 Smith. Now as to SA's if your shooting factory ammo, it just gives you 2 choices, in 1 pistol, one more accurate than the other, But if you reload, with lead bullets, ask you bullet manufacturer to size the 9 mm in . 3565" works excellent in both, .38spl, .357 mag and 9mm. If you stick with factory, expect 2 different results, as far as accuracy. Why do we want dual caliber pistol, because it has dual uses, not that 1 won't work, but it gives us extra usage and flexiibility with one pistol. The Smith 947 did not use moon clips, but an interesting extraction process, that does not rely on clips, they are collectors items now.