I don't know much about the .338 Lapua - shot a demo model AWP in the late 80s/early 90s when that rifle was being considered by the British military - but I was always surprised at how "slow" the published velocities are with such a massive case. I guess that its reputation as a long range round really comes from the 300-350(?) grain bullets and not its velocity with 250s. I take it that its the same .338 Lapua, i.e. a necked down .416 Rigby?