There is a lot of speculation in the OP's question. There are also a few factors that no one has considered in this load.
1. Does it need to mag feed? If so anything above 185gn is going to be a major compromise for seating length and powder capacity, aka speed.
2. What kind of shooting is being done? Long? Short? FT/R? Tactical Precision? Steel or Paper? A short range precision load might not be suited to ELR or Tactical shooting.
3. Cost and availability of components. IMR4064 is generally cheaper and more available than RL-15. 185 Berger's vs. 178Amax. All the speculative guessing in the world goes out the window if the shooter builds a load from Rl-15 and it becomes unobtainium for 2 years, again.
If the OP could tighten up his needs a little this thread can be a little more helpful.
All very good and valid points CanuckWR.
I'll try to lock it down a bit (at least for what I'm doing).
1. Yes, mag fed is preferred, but not 100% required. (Ruger Precision Rifle)
2. Type of shooting: F Class type, out to 600M, but may be further (1000) if I can get to the range. Most shooting is on paper, but I plan of shooting some steel out to 1000 or more (sorry, I'm not all that familiar with the exact or official names of the many shooting disciplines on the go right now).
3. Very much based on availability of components. What I have lots of right now:
BULLETS: Hornady 168BTHP, 168 Amax, 178AMax, Speer (300EA) 168BTHP(200), Berger 155 VLD(500)
POWDER: H4895(6LB), Win 748(10LB), VV N140(8LB), VV N550(1LB) IMR 4895 (2LB), CFE223 (5LB)
I'm inclined to focus on a good load for the Berger 155 gr bullets, because I've not seen much published for the Bergers. The others I have data for, but as always, your pet loads are always appreciated. No point in wasting time and money on "a dog that just ain't gonna hunt"...