I have 2 g&p mags. They both are mid-cap, and one is a 130 round mid-cap that doesn't rattle. The other one is 68 rounds that doesn't rattle. When i put about 30 rounds into each mag, it fires like 15-20 shots, and wont fire the rest. It jams with 2 bbs every time i look down the mag. These mags are brand new and I don't know why it wont fire those last 10-20 shots. Please help on why it is jamming and why it wont fire the last few shots. Thank you

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