Unless the Browning 'copy' is different from the Winchester M12, the shell placed into the magazine tube will be pushed back to a standing lug on the bottom of the breech bolt by the mag spring preassure. That will put the head of the shell just slightly underneath the front edge of the carrier. The shell stop all this time will be in the 'up' position,, not interupting the shell either going into or it's slight rear movement back out of the mag tube to that lug on the bottom of the breech bolt.
When the action is worked, the bolt goes to the rear, and allows that first shell that is against it's lug to ride along under mag spring pressure and slide up onto the carrier. At the same time the shell stop will lower and it's hook will block the next shell from exiting the mag tube while the action is open and feeding. Once the action is closed, the shell stop raises and allows the next shell to exit the tube and go back as far as that lug on the breech bolt again. No spring on the shell stop, just pivots up and down.
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I've never had a Browning M12 copy so I don't know if they're any different in this respect. I know they made a few internal changes with this and the M42. (Maybe one of them was the 'chingus'
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