Well, a good question.
My 1100 can be unloaded by cycling the receiver, to eject the one in the chamber, I then drop out the one that just ejected from the magazine tube thru the port (so I have now removed the one in the chamber and the next one to go in the chamber), then I press the latch on the bottom port, it cycles the receiver, when I pull the receiver back the next round from the magazine is ready to be chambered, only I drop it out the port and repeat as necessary. (similar to pump as already posted.)
( but I can stop here when waterfowl plug is in gun
, cause it only takes 3 then!)
I don't think I can recommend the 1100 as HD, but your question asked how to unload a self loader without chambering every round.
hope this helps,
Gfrey