I'm going to have to go with Jimro on this one. The 9.53 Saturn makes just under 2900 fps. with a 350 gr. bullet from a 27" barrel. Give it that extra 5"-7" you are talking about and you should easily hit 3000 fps. It is a 375 - 416 Improved....just what you are looking at. That also means dies are already available (no extra cost for custom made one of a kind dies
*); RCBS lists them under Group G custom dies and they run $144 for the set.
* I have an unconventional idea of my own and I know the dies will cost me.