nah, I'm trying to build exotic on the cheap :D with Shadow Ops doing the 308 lowers, soon uppers, bolt carriers and quad rail, I can get most of the components pretty cheap. So if I need to spend some extra on barrel and getting the bolt face remachined, that isn't too bad.
The 338 federal seems like it should be simple to do to add some extra punch. I'd like to do something in a 50 cal, but for that its definitely going to require me finding a machinist to make the barrel (we're still not doing that, when we build a full rifle we use FN barrels)