I just shot my 1959 Marlin 336 for the first time today. Shot really well, putting three rounds at about a 2” group at 100y with LEVERevolution ammo. After I was done shooting, I noticed one of the cases (old box of Federal Power Shock) had a split neck. Is this a safety concern? I know it’s not really a reloading issue, but folks on this sub forum are usually the most knowledgeable about such things.