Different brass, same load? That can be a no-no. If the bolt opens easily, it must be sticking in the chamber, but I don't know what would cause that and not for the Lapua. If the bolt is hard to open, you need to back down on the powder charge and start the load development over.
Been discussed elsewhere that Joyce Hornady had an issue with the 338 Lapua brass but supposedly addressed the issue. Myself, I just stay away from them. I heard the early lots sucked for extraction. I use Lapua, Nosler and PPU in that order.