I just received my new upper and the front and rear pins will not seat properly. The holes on the new upper are round. I have looked at many pictures of uppers on the EE and the holes on many of them are almost ovals. Is it usually necessay to file the holes so the pins will go through? The upper and lower are different brands. Thanks in advance for your answers.

The upper is a Bushmaster 16" CAR and the lower is a preban Kalifornia legal Oly. I know that many hate Oly, but I live in Kali, and have to dance with the girl that brought me.
edit: the upper is marked DK  Diemaco / Kaiser (C7)sold by Bushmaster

The holes should be ROUND!

You are not going to be able to pivot your upper to "open" it if they were oval.

It CAN happen that you will need to have a smith "fit" your upper to your lower. Or that you may need to "fit" and the takedown and pivot pins; mag release button; bolt catch, etc. to the lower reciever.  I just do not know if that is always the case with name branded uppers and lowers that are supposed to be milspec.

Either way, once it is filed and fitted, that will not affect the reliability or function of your rifle. The only hassel there is the need for you to bring your upper / lower to the smith and have it fitted AND have the same re-finished again.