I am prepared to eat crow.
I know this thread is older, but I feel the need to say mea culpa. I was wrong.
My American Browning 12g is now on the workbench with the bolt removed from the receiver and disassembled. This particular receiver has no notch at the bottom of the ejection port. When I got the gun it was packed full of grease. Between the lack of a notch and the excessive grease, I could not see the assembly pin on the bolt. The only reason I can now see the pin on the right side is that I've been trying to clear grease out of the receiver, of course with the bolt in place. I saw what looked like dirt on the bolt, but it would not come clean. I then realized the dirt was in fact the pin.
To remove the bolt, it was necessary to use the smallest punch in my possession (as I could not get a more appropriately sized punch between the receiver and bolt) to push the pin backwards toward the left side of the receiver. Once the pin cleared the outside of the receiver, I could grab it with pliers.
Again, I was wrong. I've seen many requests online for this information, but nothing indicating how to remove the bolt from this particular variant of the A5 design.