Some of the slides of the pistols do not travel back enough when locked back, they do not line up with the slide catch. The Glock and the 1911 slides do not travel back enough as shown in these images:
Glock: https://pbs.twimg.com/media/CWWqLC4WoAAEa6A.jpg
1911: could not get a hold of screenshot yet.
Real Glock 19: http://www.tannersgun.com/images-glock/glock-19-pistol-slide-back.JPG
The Barrel on the Glock also needs to tilt up when the slide is locked back or in the backward position.