I gave the only 420 I ever owned (a 20 gauge) to my nephew so I have none to examine. I can picture this gap y'all are talking about, but I'm not sure I understand if it effects lockup of smaller barrels in a larger frame. Is there side to side movement with the smaller "orphan" barrels or do they lock up tight in all directions?

"You can lead a man to logic, but you cannot make him think." Joe Harz
"Always certain, often right." Keith McCafferty