In general you're correct, the higher mass of .22 contributes to a higher BC, but my point was in reply to a particular theoretical scenario: This particular scenario would only be true in a vacuum. In air, the .22 would actually have a worse BC. Same mass but bigger pellet so there is more drag. An extreme example but if you imagine a ping pong ball with a mass of 3 grammes and an 8mm lead ball of the same mass, launched at the same velocity, you'd never expect them to have the same trajectory because the ping pong ball has hugely more drag. As I say, in the real world the higher mass of .22 pellets gives them a better BC.