The PTS EPM1 magazine is the latest mag coming from PTS to be one of the highest capacity magazines that do not require winding.  Being know for their exceptional work with polymers, the EPM1 is rugged, works with many different platforms, and claims to be incredibly consistent when feeding bbs to your AEG.

PTS 250rds Enhanced Polymer Magazine (EPM1) for AEG
Polymer Construction
250 Rounds Laoding Capacity Magazine
Orange mag level indicator
Low friction internal shell
High efficiency compression spring
Unique magazine mag well guide that reduce snagging
EP dot pattern texture for better grip
Best accompanied with Plastic Bullet Loading Too or Speed Loader
Suitable for 6mm Plastic Bullet only
No more Plastic Bullet shaking which essential for intrusion during airsoft combat situation
Polymer Magazine Base (with Angled Surface and Dot Matrix)
Suitable For Marui, KWA, G&P, ARES, Krytac, Umarex (VFC) M4 AEG/ PTS PDR, ERG, Masada/ Amoeba AM Varients