I have used Lapua brass in 6.5x55 and recently loaded some .308 brass with 168g Sierra's. The 6.5x55 brass doesn't fit my Barrett Fieldcraft but does work in my wife's Ruger. Rim size is too big for the Barrett The .308/Sierra combo is the only loads that didn't need straightening. Almost no runout for 50 rounds. All I did to the brass was make sure the necks were round and chamfer.
Maybe that Lapua brass is just meant for sloppy military rifle chambers. Send it to me, I'll use it. This is how mine works. Testing some loads last weekend in prep for a military rifle shoot coming up next month: