Lupua brass issue

[popgun]

I agree with most that the Lapua brass may be expanding a bit at the head and your die is undersizing the body to much and bunching/deforming the case head. I use a bit lighter charge when loading Lapua brass and I use a Mighty Armory sizing die that doesn't squeeze the body down as much. It also has a much better finish inside the die. With Hornady brass I use 28.7gr of Lever and with Lapua brass I bring it down to 28.3. Haven't had a problem.