Originally Posted by Styrak
You are correct on the first part, cocking the hammer with no BB chambered and a mag full of BB's will cause blowback and a round to be chambered.
It will not hurt the gun to release the slide with no mag in. It has the same effect either way.
Okay, so instead of racking the slide after inserting a fresh mag, one could just fire a shot to chamber a BB... less realistic, but less time sonsuming than racking it... in the heat of battle it wouldn't change a thing, as when you reload, you will either still have a BB in it, or have the slide locked back, so you would have to use the slide stop lever anyway... but in theory it is possible...