Technically yes. (After a couple hours chat with Stalker
). If you put heavier bbs in a gun the bb will take less affect to the wind and the travel. Here is an example. Say you are using .12g bbs, you shoot, they go flying becuase they are to light, although they give you insanely high fps it gives you zero distance and accuracy. Now lets say you are shooting .43s in a GBB, the bb will shoot more accurately and give you more distance due to the extra weight. If you want to have the same FPS as you would be shooting .20s upgrade your gun slightly to compensate the extra weight of the bb. If you think about it, its not only about the upgrades in the gun, its also the ballistics (bb weight, wind, hopup) that make your gun shoot farther. (Thanks Stalker
)
Edit: Yes and no actually. If the bb is too heavy it wont go far at all.