I'm thinking about getting one of those, do the mags cooperate in standard pistol mag pouches?
Eh...they're iffy with mag pouches, I can get them to fit in a standard 9mm Eagle Industries Pistol Mag Pouch, but it's tough.
I just sold this Five-seveN.
It's a great GBB. Accuracy and range are amazing. Blowback is the hardest I've experienced, but that also causes problems. Extended use of Green Gas/Propane with the 5-7 will cause parts to crack or explode. But, I wanted something I won't have to baby out on the field.
Here are some more pictures for you guys to look at :

