Posted this on another forum, but couldn't get an answer:
Hi All,
I am trying to figure out the function/purpose of the hook which is rotatably mounted on each hammer of a Winchester 101 Pigeon Grade XTR Lightweight 20ga O/U. (The part in question is noted by the writing pen in the photographs below.)
The hooks are able to freely rotate, and are not actuated by any spring or other mechanism, as far as I can tell. It seems that only gravity or inertia would cause the hook to pivot on its axle. In fact, I can hear the hooks rattling around inside the action when I turn the gun upside down or shake it. Seems like these things would violently rattle with each shot, and eventually cause some damage to themselves.
I think the normal position of the hook before firing the barrel is as shown in the first photo. The hook engages the pin (as shown in the second photo) when the gun is turned upside-down.
The hook does not hold the pin tightly when engaged with the pin, i.e. there is quite a bit of play between the hook and the pin. I have verified that with the gun upside down and the hook engaged with the pin, the sear can release the hammer when the trigger is pulled, but the hook prevents the hammer from falling and striking the firing pin. The hammer only moves about 1/8". The hammer is then cocked when the gun is broken open, but the shell (snap cap when I tried this in my basement) is not ejected.
The triggers are mechanical resetting. Operation of the safety or barrel selector does not appear to have any affect on the hook.
Especially perplexing to me is that not all my Winchester 101 Pigeon Grades have this feature, and none of my three exploded 101 drawings show the hook.
I guess this could be a safety feature to prevent the gun from firing when it is upside down, but this seems like a lot of extra complication (and manufacturing expense) for a safety feature with a relatively narrow range of use. (edited to add: could possibly be a safety feature to prevent the gun from doubling, or from firing when the action is closed hard?)
Thanks!
--shinbone

