My buddy loves Grand in his 7mm PRC with 175gr ELD-X's. 2920 fps avg with ES of 28. It's only a 22 inch barrel and was easily 3/4" at 100 from his Bergara.
What's the barrel's twist rate? Hornady recommends a minimum of 1:8.5 for that bullet. I don't believe most factory Tikka 7 RM's have enough twist for that bullet.
I've wondered about the x-die but haven't got one. I will say, I've never had an issue with any RCBS product. When I've had questions, their customer support has been awesome.
@Kib you answered your own question. The bullet had a different profile and just needs to be seated to work. Recommended COL's in manuals are just that, recommendations. You may have to seat certain bullets longer or shorter depending on your gun. There is nothing "wrong" with the Partition...
Couldn't hurt to experiment. I've used regular primers with Staball HD in the 6.5 PRC and magnums for the 7mm PRC & 7 Rem Mag. I might try mags in the 6.5 PRC just to see.