Just about every shooter owns, has owned or will someday own a Mossberg Model 500 shotgun. Like a Winchester Model 94 or a Ruger 10/22, the old Mossy is just one of those guns that endures forever while newer designs come and go. It’s always been a snap to swap Mossberg 500 barrels, and now it’s literally a snap to swap out just about everything else. The Mossberg FLEX 500 is the most modular shotgun system ever made. It’s the Stoner 63 of pump-action shotguns. Is that cool or what? . . .