The British Clabrough I mentioned is I believe built prior to 1900 for the American market. It is a backaction sidelock, does not have rebounding hammers & can be loaded or unloaded without forcing it open further after it cocks. An American Baker Black Beauty 16ga back action side lock does have rebounding hammers or seems to as when fired & disassembled the pins do not protrude from the breech face. When cocked & released the barrels are well clear of the breech for Un/Loading. All of my Lefevers are timed so the main spring tension is arrested at the point the pins are flush with the breech, leaving the hammers free to travel on until stopped by the pin itself. This is not a true rebounding hammer but serves essentially the same purpose. On all of them the barrels are clear of the breech when cocked. I would not want it any other way. If you want to check to see if you can fire one by "Slamming" it without it being cocked simply put in a snap cap or a primed empty.
I ""NEVER EVER"" walk around with a gun broken open with shells in it, so them falling out is of no concern to me. If in the presence of others I feel the need to open a gun I also unload it. If in a hazardous footing condition I do not feel comfortable navigating with a loaded & closed gun, I Stop, Unload & re-close the gun till I reach a point I feel comfortable with reloading it. Although fortunately I have not proved it, I personally feel that should I take a really serious tumble the gun will have a better chance being bolted shut than with the barrels free to flop & perhaps put a heavy twisting force upon the hinge lug, just my thoughts on the matter, therefore I simply have no cause to walk around with a gun having the barrels swung open & shells in them.
It is a very simple matter to ensure that both barrels are cocked when loading. "IF" either hammer is un-cocked the gun will have to be held open to load. One simply opens the gun until it stays open & its Cocked. No big deal here, Theory is fine but Practicality is often far better. Being able to load without having to hold it open is just far more practical as I still only have two hands, not three & I don't always have a rail fence handy to stick the barrels under while I load.