Hey All, I loaded and shot 85g Sierra HPBT in new .243 Lapua brass tonight. Same bullet, powder, primer and seating depth. Only change in load was powder charge, which was VVn150. No issues at the range and found a nice charge for that bullet. My question is this.. When I got home I calipered the brass and expectedly the length and neck size were a few thousands over the new brass as one would expect being fire formed. The used brass still measured within Sammi spec, still chambered in my rifle, still fit in a Wilson chamber checker BUT did NOT fit in a Lyman chamber checker ever so slightly but could be pushed in. I checked the shoulder in a RCBS precision mic and it passed Sammi as well. Actually 2 thousands under Sammi 0 on the RCBS. Case length is still under as well. The neck diameter did open up about 3 thousands, which I think is the Lyman cartridge check issue. All this being said, and if sizing is recommended I will FL size, do I need to resize? It's not that I do not want to do it I am more interested in the process and seeing if shooters don't resize in this type of scenario. BTW best grouping was 36.5 g VV n150 at 3k off the lands which gave a 4 shot group of 1/4" and 1 flyer making it a 1-1/16" group from a TC Dimension.
I apologize if this has been covered but when I had the time to research resizing I didn't know what questions to ask and now with an 8 month old shooter in the making, it proves difficult to get on the forums. Thanks for any info/help.
K

You can neck size them only if you prefer. But the neck has to be re-sized to hold the bullet.

If it will still fit in your chamber then yes, just neck size to hold the bullet. All those gauges are useless. Your chamber is the gauge.

Thanks guys, saved me a bit of time on that one.No matter how much you watch or read there is no substitute for doing it and getting the process going.

Neck size only. If it fits your chamber, Full-length sizing is not needed.
Lapua brass will outlast most any other brand and will hold up with neck size only for nearly a lifetime. At some point, you'll have to trim to length as the bras stretches.

Thanks Doug