Large rifle primers won’t work, the cups are a different height than large pistol primers.
I don’t load anything but the above mentioned 10gr Unique under a Keith bullet anymore. But I have in the past and one of my notes in my load book is for the old Hornady 240 JHP over 9gr of Unique. I believe an older Hornady manual I have showed that load. I can’t think of any reason it wouldn’t be fine under the XTP. PowerPistol is another good powder that is similar to Unique you might keep an eye out for when shopping.
The 9-10gr Unique load isn’t really a reduced load, more like a mid range load that will give between 1100-1200fps depending on barrel length but it is much easier to shoot with the reduced blast and recoil plus no giant fireball that some factory loads produce. I have shot through a 6 foot black bear diagonally with the 9gr load and pigs up to 300lbs with both the 9 and 10gr load, some of them lengthwise, I’ve never caught a bullet. To my way of thinking it’s really all that’s needed.
