if you look at the middle of an mp7 40 round mag you'll notice the flare at the sides of it where it would mate with the pistol grip. that flare is the hassle in fitting into an mp5 pouch. depending on the pouch it'll snag at the mouth of the pouch. thus the looser fitting the mouth of the pouch is the better for an mp7 40rd mag. if it's really well fitted for a single mag than you'll fight with it on the way in and out.
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