As far as Glock .40 pistols go, there are several reasons why you can get KB's:
1. Higher pressures the .40 S&W can generate
2. Unsupported chambers
3. The ability of the Glock to fire out of battery
If either of those factors were removed the instances of KB's would drop dramatically. That's why I prefer my Glocks in 9mm flavor, you don't hear of them KB'ing very much. While reloads likely are more common to cause KB's, they can occur with factory ammo as well, which has been documented. But a overcharged reload or factory load would undoubtedly increase the risk of a KB in a Glock or any pistol for that matter. Fortunately, if a KB occurs in a Glock, it's usually not too severe from what I have seen and heard, at least as far as severe injury to the shooter. But I wouldn't want it to happen in the middle of a shootout.
-CH