I have a couple of these 410's and have owned several over the last 20 years or so. I shoot commercial shotshells from it no bother and with lots of practice (and the second shell held in the mouth) have managed to get a 'left and right' when skeet shooting with one.

I have found that the .410s manufactured or at least dated POST 1948 seem to be chambered for 3" shells and those from before that date are chambered for the formed 303 cases and approximate to 2 1/2" commercial shells. That is just my experience with a very limited data set of about 10 -12 items.