I have read that other people have had problems with the Remington brass being oval shaped after being shot. I am just woundering if this could be the problem..
Well after you run the shell through the resizer it would be put back into spec so I doubt that is the case.
Ok you are using interlocks correct? has the interlock ring which doubles as a canilure on the outer surface of the bullet . I'm guessing you are using a crimp, I will put my money on it that you have your crimp die not set properly either set to far down or tomuch crimp either could deform the case neck or shoulders. try backing the crimp die out a 1/8 turn see if that works if not back it out another 1/8 turn or keep backing the crimp out untill you get it to work. Cartridges shot from a rifle need little to no crimp. I dont use any crimp at all. except for on cartridges that will be loaded into a tube magazine.