Would also mention that IIRC correctly The 1897 also has no safety block on its external hammer and can result in AD if struck or dropped on hammer. Case in point: Early 70's as a young LEO witnessed an older officer going on duty carried his gear to to his assigned vehicle. Had 1897 and heavy metal briefcase, opened the car door slid the shotgun across the seat, threw the briefcase in behind it and BOOM! Blew a jagged hole out the side of the car door. Well, they always told us to learn from the more experienced officers so from that night on I made sure to only checkout a Rem. 870.
In a loaded '97, with the hammer all the way down,,the firing pin is resting on the primer of the cartridge and under mainspring pressure. The firing pin was made to extend from the face of the breech block when the hammer is down. As the Officer found out,,not a safe way to carry the '97 loaded. BTW it's the exact same situation that the Winchester leveractions ( '92,94,73,86,etc) use but w/o any bolt release mechanism. Marlin leveractions too.
The hammer placed in the half cock position was the proper way to carry the '97 with a chambered round. Also, in that position, the bolt is locked shut and the action cannot be opened. All this assuming an action in proper mechanical repair and adjustment.
There is a firing pin block in the bolt that engages the pin as soon as the bolt is unlocked and holds the pin in the rear position until the breech block is once again closed and locked. This is to avoid the shotgun fireing with the breechbolt in the unlocked position. This firing pin block mechanism depends on a small spring and cam surface to work properly and on several guns I've worked on it wasn't working properly.
A simple check on the F/P Block is to see if you can depress the fireing pin at the rear while the bolt is retracted/open. The tip of the pin that the hammer strikes should be slightly retracted from the back of the bolt and should not be able to be pushed forward into the bolt at that point.
Also remember with an 870/1100 or any of the other 'hammerless' pump or auto shotguns out there that in most all the guns, the internal hammer is at full cock with a round in chamber and the 'safety' is only a trigger block and in no way blocks the sear.
Wow... 
