Keep in mind too if you took your gun with a mag with 0.20s, and then another with 0.25s, chances are the 0.20g bbs will be less affected by the hopup too. The 0.25s will push for longer, and push harder, upon the hopup then the 0.20s. I think so anyways.. lol.
EDIT: My point is that there are a lot of different things that come into play as to how much the speed will change when you change the BB weight.
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