There are much easier and cheaper ways to get to a 400 point blank rifle using a 10" target. This does not require an over the top wildcat. You can very easily achieve a 400 PBR rifle with a 300 RUM. Much cheaper and easier.
A really hot 30 such as the 30-378 (right barrel length and twist), 30-338 Lapua IMP, 308 Warbird etc... are more like 450 yard PBR guns (10" Target).
Now if you like to play around with wildcats, etc....Then that is a different story. I used to toy with the 30-378 years ago and a buddy of mine toyed around with a 30-338 Lapua Improved. Both were beasts. Both were fun but we quickly outgrew them due to the cost of opperation and barrel replacements.