Not sure if this will help much but i have a couple of CYMA Mid Caps running on my G&G P90 and work great when other makes did not feed correctly - ive gone through a few makes of mags for my P90 and found that the feeding issues (for me anyway) are down to a very slight difference in length and putting 2/3 strips of PVC tape on the end helped push them back enough to feed correctly, but for me i did not need to do this with the CYMA mags