I heard some do this. I was told my barrel will take a few hundred rounds to “speed up”. So if that’s the case, would expanding the necks be a mute point until I really start reloading after my brass is fire formed?I mandrel expand new necks to fix the bent mouths that inevitably happen in boxed brass, even Lapua. I use the LE Wilson new mandrels, which should result in an ID of 0.0015" under caliber on new brass:
I also use the 21st Century set in 0.0005" increments for reloading cases, but I like the LE Wilson for new cases.
Sorry, lol, meant to say if the brass grows a lot during fire forming, in my experience, it will need to be fire formed before development.In my experience, if the brass doesn’t grow very much then resizing can get you pretty close but if it grows a lot, I wouldnt go through too much trouble. Maybe get a rough idea on velocity but it’s going to be off from a correctly sized