When it was working properly the spring, ledge and screw were supposed to keep the wedge from being lost. A "wedge" is wedge shaped so if it got bumped in a holster or loosened during firing and fell out the gun was rendered useless.
Thanks for the explanation, after I posted my question I got to looking and see that your right, even when pulling the wedge for breakdown the screw will catch the spring keeping it from coming all the way out or sort of if ya don`t pull to hard.
Over the years I`ve heard different thoughts like the screw is adjusted out to keep the wedge from going in to far too the screw was backed out to remove the wedge.
I`m afraid if the wedge backed out far enough to catch the foot on the spring the poor guy would loose more than the wedge, possibly the whole barrel.