Its called a Hicap (High Capacity) magazine and is designed to hold a lot of bb's at one time. As such is uses a manually operated wheel on the bottom to basically push up the BB's that are then fed into your gun. The advantage of a Hicap is that it holds a lot the downside is what you're experiencing. Most players including myself frown upon them and go out and buy Mid caps or low caps. Mid and Low caps are self feeding due to an internal spring (no winding a wheel). To give you an idea hicaps can hold between say 400-2000 depending on the style where as mids usually are 80-120 and lows between 20-30 ish. Low caps are predominently used for hardcore reinactors or full mil-sim players. The standard by most players is mid caps. So in short save some dough, buy some decent mid-caps and lose the hi-cap.