The manual is the (Lee modern reloading second edition) and the only one I see a warning for is the 40 S&W.
It may have been some early models, I don't know anything about a Glock but the warning says---
"Do not use reloads in Glock or similar guns with chambers that do not fully support the cartridge due to the intrusion of the feed ramp."
I thought just as some of you stated, that if the ammo was loaded right, it would be fine.
Just never saw this type of warning before.
Thanks, Blu