If still loaded, drop mag, place on safe (if equipped) secure (knees only in my view)with muzzle pointed safely away, insert mag, re-grasp, continue mission.
All this done preferably behind cover, even if still fully capable.
God Bless & MOLON LABE
I was talking with a neighbor after supper and he said the easiest way he knows is to dump your magazine before the last shot and slap in a fresh mag. You may waste a round or two that way but it sounds good to me.
He’s tried other methods and wasn’t able to get the slide back far enough to reload a round. He’s changed magazines, then held onto the slide with his free hand and was able slide it back. He didn’t like that method because he felt it was too dangerous.