Hi John, HGA is something that came from a vendor's system - they use it to designate items as handguns - it doesn't mean anything as far as the gun itself.
5lb represents the 5.5lb average trigger pull.
Stay safe & have a great day!

Hi John and welcome. In summary: An "HGA" designation on a Glock pistol is not a standard Glock model, but rather a distributor-specific label used to identify a particular configuration or feature set of a Glock pistol offered by a specific retailer. Example here (reduced dimensions): https://heroquartermasters.com/product/web-glock-19-g19-hga-9mm-4-0-bbl-fs-5-2-10rd/ -- Cheers stay safe and enjoy!

HGA stands for "High Grain Ammunition," indicating a heavier bullet weight, typically around 147 grains.