That's quite normal with H4198, and about the same with Re-7. AA2200 is the best powder for full velocity loads. By the way if your chamber was cut with Todd Kindler's chamber dimensions, your Lapua brass is going to be larger at the head than the chamber dimension there. Lapua 221 brass is .3755" and the Kindler reamer dimension is .374", just an FYI.
Not sure what reamer x-caliber uses. What if it is .374 at the head??