Bob,
A few years ago I went through my loading notes and averaged all the 3-shot groups fired with Nosler Partitions, from 60-grain .224's to 400-grain .416's. That's ALL the groups, not just from the loads that shot most accurately, and the average was 1.01 inches. That may not win any benchrest contests, but it's generally good enough for big game hunting, especially in Africa where paying the trophy fee if something is wounded and lost seems to cut down on longer-range shooting. (Well, and often not being able to see anything beyond 200 yards in a lot of thornbush country.)
Probably the 60-grain .224 Partition has given me more trouble than any other, but eventually found a faster twist than the typical 1-14 of .22-250's and many other .22 centerfires normally gets it into an inch as well.
Like you, have also generally found Partitions shoot best with maximum loads, but as the head bullet designer at Nosler suggested many years ago, a slightly faster powder also often helps. It doesn't always have to be "fast," just something like one of the 4350's instead of H4831 or RL-22.
The first big game load that consistently put 5 shots under an inch at 100 yards from one of my rifles was what would be considered too much IMR4350 behind the 100-grain Partition in the Remington 722 .257 Roberts inherited from my grandmother. The muzzle velocity was well over 3200 fps from the 24" barrel, but primer pockets in the Winchester brass remained tight, and bolt lift was easy. This was long before laser rangefinders, and I sighted the rifle three inches high at 100, which turned out to be dead-on at 300. This came in handy when backing up pronghorn hunters I was guiding, especially when I learned how to use my scope's reticle as a rangefinder.
At the other extreme, CZ 9.3x62 groups three shots well under an inch with 286 Partitions, and my Whitworth .375 H&H does under an inch as well with 260 Partitions, but "only" about an inch with 300's. My CZ .416 Rigby likewise does about an inch with 400-grain Partitions and Nosler solids--but that's with a scope, and I only use a scope about half the time. With the express sights it shoots Partitions into about 2 to 2-1/2" inches at 100 yards, which has been accurate enough for buffalo at under 100.
Of course, like you when working with Partitions (or any other expensive premium bullet, whether Barnes TSX's, Swift A-Frames or whatever) I start with a cheaper bullet of similar weight, usually either a Hornady Interlock or Sierra GameKing or ProHunter. When I've found a powder and charge that works pretty well, then I switch to the more expensive brand, and almost always find it will shoot with a similar load.
