Look closer. All 10mm rounds fired from a glock will have a small bulge at the base of the brass. I've been told you can get an aftermarket barrel that will solve this problem. But you sacrifice feed reliability.
Take your barrel out of your gun. Then hold it vertical with the muzzle down. Drop a live round into the chamber and look at how much of the cartridge is unsupported at the top of the feed ramp. YOu might need a flashlight to see it. This is where the case will bulge and sometimes even rupture.
Glocks are notorious for having such a deep ramp carved into the chamber. This is what makes them feed so reliably. also, they seem to have a very loose chamber. Wiggle the cartridge around in the chamber and see how loose it fits. This also is done on purpose to enhance feeding reliability.
Glocks are not a good choice if you are a handloader. Well, at least a glock with a factory barrel isn't. If you plan on saving your brass and reloading it, you should get a different gun, or else get a different barrel for your glock.