I have an early gen2 19 that came with the original glock mags. They drop free when empty but do not wirh rounds in the magazine. GLOCK designed the mags without the liner so they would swell just a little when loaded to prevent inadvertent magazine releases. The early Glock 19 also had a u shape cutout in the front of the grip and the cutout in the rear to make pulling magazines from the gun easier.Been discussed befo. Rumor/story has it it was an Austrian feature designed that way. Apparently Americans hated it because we train to "drop free" mags on reloads (not sure where that came from), so then Glock decided to make drop free, steel lined mags that don't expand when loaded with ammo.
It's a terrible "feature", a mag that doesn't drop free. I'd like to hear why you think an empty mag that doesn't drop is a good thing.