Thanks for the photos. Very interesting. And thanks as well for the choice of handgun. The Benelli MP90. I have an MP95 Atlanta and these nice handguns just don't get enough air time or review time.
But I will add that it may be the design of the Benelli that adds to the detritus of unburned powder leaving the barrel in that it's actually only 3" long. I've always wondered how such short a barrel can be part of a design that is so accurate, but it must be true that such a short barrel contributes to the likelihood of more unburned stuff than a Model 41 or some heavy-barreled Ruger.
B