This problem occurs when using the ‘Enable Weapon Fast Switch’ option under the Black Mesa tab of the options menu OR when using the ‘Last Weapon Used’ key (default q)
If you press the reload key and then change weapons with one of the methods listed above the reload will be cancelled. but the reload sound will play in its entirety. Reloading another weapon will cancel the sound of the previous reload, shooting does not cancel the sound of the previous reload.
This problem occurs with the Glock, Magnum and Assault Rifle
This problem does not occur when changing weapons via the scroll menu (when Enable Weapon Fast Switch is disabled)