the only ammo i shoot for my 450marlin is hornady custum 350gr.
i have had problems like that before but the shells were rusted and had problems feeding and taking out when shot.
i always check the ammo before i buy my ammo ever since.i was cleaning out my gub safe and found 6 rounds 250gr. 35whelen core lokt's. out of the 20 rounds, those 6 were discolloered ( brown casing ) and the bullet was not as shinny as the others and looked like it was like some rounds that where sitting in my truck for about a year. i wonder if this could cause accuracy problems or shooting problems shooting them.