In Grave/Digger , you can usually swap gun hands/sides while aiming by pressing F. One Reddit guide also says flipping your camera view with F makes the gun appear on the left side.

Quick steps

  1. Equip and aim your gun.
  2. Press F to switch the side.
  3. If it does not change immediately, try flipping the camera view first and then aiming again.

Controls note

The same community guide says the main gun controls are M2 to aim, M1 to shoot, R to reload, and T to check ammo.

TL;DR

Use F while aiming to swap sides in Grave/Digger.