I have the Savage 338 Lapua and I am having issues with the fired brass not extracting.

I am firing Hornady match grade ammo, 285 gr butllet

I first fired 10 rounds to site in, no issues.
Next I attended a 2 day sniper class and fired 180 rounds, the last shot the brass would not extract.

Brought the rifle home, cleaned it, went back to the range.

I fired about 60 rounds and 1 out of 6 would not extract, 10%.
Some of these were really stuck, others popped out easily with the bore rod.

I have done a search and some say to get the chamber polished, seems like an easy and inexpensive fix and I will get it done.

Do I have an ammo problem as well ?

I want to reload the brass, but I don't want to see this issue whan I go back to the range.

Your thoughts ?