To drop the magazine for the majority of the firearms in the game you will press either the "A" button on the Right controller or on the Left controller "X".

To rack the slide forward on a firearm you will press the "B" button on the Right controller or "Y" on the Left controller. ( there is currently a bug where after some time you will not be able to rack the slide with the buttons in this case just put your hand over the slide and press the Grip button)

To leave any game mode,go to settings,reset the game mode or see how many kills you have you will have to look at the watch that is located on your Left Wrist once you are looking at your watch you will have to tap it with your hand then choose whatever option you want to.