(Capcom's primary storyline)
The Glock 30 is a sub-compact variant of the Glock 21. It is fed on ten .45 ACP bullets.
During the 2005 Harvardville Airport terrorist attack and subsequent Air Dome Laboratory Incident, US-STRATCOM agent Leon S. Kennedy was equipped with this handgun. He then gave this to Claire Redfield.
Leon's choice of using the Glock 30 as a backup is rather odd considering that it is a .45 ACP gun while his primary weapon, the Silver Ghost is in 9mm. This means that he has to carry two types of ammunition instead of both his guns sharing the same kind of ammo, which is more convenient. However, it also kind of makes sense to carry a gun in the caliber of .45 ACP if he is expecting targets that may need the bigger bullets to take down while still being compact enough as to not hinder handling performance.