Without UI and without any keybindings, I am unable to identify any way to switch the secondary weapons in Metro: Last Light in Ranger Hardcore. Without using the UI, how can one switch between secondary weapons?
Figured it out. The UI isn't visible, but it is present. With the default keybindings, hold TAB, then move the mouse left for grenades, right for incendiary grenades, up for throwing knives, and down for claymores. There are also sound cues to signify which has been selected.