Pressing Shift+m/a/r/o takes you to the Left Ring/Ready Hand/Bracers/Neck equipment slots instead of assigning Default Melee Weapon/Ammunition/Ranged Weapon/Off-hand Weapon.
Which means you can't use '-' to quickly switch between your assigned Default Melee Weapon and Default Ranged Weapon.
Likewise when picking out feats; pressing K (shift+k) has the game select the feat listed under k.
Pressing shift+arrow keys DOES however give the message "You must select a default projectile before using the ranged attack shortcut.".