Have you had the head space checked in that rifle? I've seen that happen in the past with guns with excessive head space.

I've also seen it when a handloader, pushed the shoulder back too far when resizeing the case, creating excessive headspace.

Over the years i've found factory ammo with the primer up side down (pistol round), the primer side ways and crushed (Federal), bullets seated so lopsided the round wouldn't even chamber (Winchester), and all sorts of other things!!

I even had a "new" Ruger 357 mag. revolver come in, that the cylinder wasn't chambered all the way down!! It would only allow 38 spl's go in less than 1/2 way!! How did they test fire that one???????????????