When it comes to initial case preparation I’m a firm believer that full length resizing is something that should be avoided. I know guys that do it, which is fine, but I do not and feel that it should not be a part of the initial stages of new brass prep. Make sure right off the hop that it is not a COAL issue. If your COAL is not excessive it might be the brass. There are some instances where new brass does have a crush fit, but they are relatively rare. I am a bit surprised that is happening with Lapua brass, but it could happen. Another issue is excessive case length but I have never seen that in a new case ever. But I’m sure it could happen. If it is the case neck, a more likely scenario is a burr at the case mouth. That can cause issues with chambering and I have seen that.
There are three issues that can result from resizing new brass. One is concentricity (good and bad), two is headspace issues (more common than you think) and three is unnecessarily work hardening your brass. Unless you have the tools to measure these two things, avoid the practice. I’m also a bit stumped as to why people believe that their $30 FL resizing die is somehow superior to what Lapua might have in their factory.
Trimming new cases is not a horrible idea. Some batches of brass vary so much in length that I have, in the past, trimmed all brass to match the shortest OAL. Consistent bullet release is key to accuracy. Neck tension matters, and neck length affects neck tension. Again, not something I would consider an issue with Lapua brass.
My initial case prep goes as follows:
I lube the inside of the case necks with Hornady One Shot on a Q-Tip and let them dry. I have used graphite but I have experience galling and don’t use it any more. Then I run all of them over a Sinclair neck turning mandrel. The neck turning mandrels are two thousands under bullet diameter and I personal prefer that to the one thousandths of the neck expander mandrel (all my mandrels are chucked in a drill and polished with JB or Iosso bore paste). After expanding the neck I brush the inside of the neck with a bronze bore brush and then chamfer and de-burr the case mouths. Then I prime, add powder, and bullets.
If you are experiencing crush fit with the odd case, know that pulling the trigger fixes that problem going forward. Don’t fret about it too much.