Thread: 338 lapua issues.

I have no experience with this calibre.

Vivid is your friend, fl sizing if set to long for head space can squeeze the body in pushing the shoulder forward and making tight headspace...or rather head interference, especially if there is a large difference between body dimensions of fired brass and fl die.

The opposite is also possible where the fired brass body is quite expanded and your fl die is not small enough/brass is to springy to bring in the body to fit your chamber.

Colour in a strip with the vivid marker down the length of the case and try to chamber. You should be able to see the tight spot on the marker and deduce if it is a headspace(wind die down) or body issue(new smaller die or new brass)