Martin- here is Pedesoli's breech. Note the nice 'fence' that is not doing the job it was designed to do - to protect the shooter from cap fragments. The nipple seats are too high and the nipple itself prevents the hammer nose from curling over the fence as the original design calls for. It would be sooooeasy for them to 'fix' their design. There is no drop to the nipple seat at all, into the standing breech.
Below, is an original H.Wahl gun showing a nice 'fence' and the proper curl of the hammer's nose over that fence to protect the shooter from cap fragments. Fences, are to protect people - from animals, protect children from traffic and protect your eye-balls from cap fragments. My wife wore a small 1/8" fragment of piece of copper in her eyelid for many years, little grean spot visible underneath the skin, befor eafter abotu 15 years, it worked it's way to the surface. Had here eye not been closed (probably flinched at the shot), the frag may have struck the eye-ball itself.

To fix? Well, if enough threads are visible when you remove the nipples, you may mill the surface of the nipple seat itself down. you can use a shorter nipple and you can also drill the hammer nose out a bit so it comes down farther other the cap.

I knew saving that pedersoli double-gun picture would come in handy, some day. Rather graphic, their cost cutting venture shows. It would have been a simple matter for Pedersoli to mill the nipple seat to the correct level - simple and cheap - they didn't. Too bad. It would have greatly improved the appearance of the gun. Most modern made double shotguns are the same.