By charger you mean magazine, right? All high capacity magazines have the wheel on the bottom that you have to spin to maintain spring tension in the magazine, since they feed from a large reservoir of BBs and not a single continuous tube. The lower capacity magazine should hold around 50 BBs, and it probably feels cheap because it's made out of plastic, where the hi-cap is made of metal. Not as realistic, but cheaper to replace when you lose them in the field.
I'm not sure what you mean by the gun feeling weak. It should be shooting around 330-350 FPS, which is actually a little higher than average for an unmodified gun. If you're talking about recoil, I'm afraid you're going to be disappointed, as electrically powered airsoft guns typically have little to no recoil.
You should be able to unscrew a couple of caps on the dot sight (it varies from model to model) to access the elevation and left/right adjustments.