Soup,
Keep me informed of how that barrel does! I've just put on my 7.62x39 15" barrel for spring (had my .44 mag barrel on for deer hunting last fall). I've just started working up some loads. I'm going to try out some Speer 100 gr. Plinkers for groundhogs. It might be a few weeks before I get to shoot them, but I'll let you know how it does. Not sure if the twist rate will be right for that light of a bullet, but we'll see.
Not sure if you're aware, but different companies use different primer sizes in that round. I see you're using Lapua. Lapua, Winchester, and Federal use large rifle, Remington uses small rifle. I have some once fired PMC stuff, but the primer pocket is in between--too big for small rifle primers, and a little too small for comfort with the large rifle.