10-round Glock mags are reduced by a shallow V-fold in the steel liner, which is molded inside the plastic mag body.
It prevents the rounds from nesting in a normal double-stack configuration.
There is no getting around it!
I'm going to tuck this little tidbit away .... Just in case.Actually there is one way around it. If you own a G-17, buy 10 round G-22 mags. They hold 15-16 rounds of 9mm IIRC. They fit and function just fine in 9mm guns. Same with 10 round .40 mags working in 9mm Sigs and Beretta. Would also work in the old P series Rugers. Not sure about the SR series of Rugers.
Or even better why not put a 9mm follower in the 10 round G22 mag body?