I use a 140 grain Sierra Game King bullet in my 6.5 cm. Once I finished my H4895. I tapped into my IMR4895, more or less, to run out the 1 lb. bottles. The IMR4895 shoots fantastic, and I really can't see how I could improve on accuracy with anything. Based on what I had read, I picked up some Varget, a 2nd choice, only because it was available at the time. I haven't tried it yet.
I will make some ammo using some IMR4350, H4831sc, and Varget and see how it goes. That H4350 is always on my mind as a must have.
The fast and slow is what trips me up, so now, even though I've read it before, it makes sense. That explains why my switch to a 26" barrel on my .270 shot so erratic with the same H4831 load. Once I dialed it in, it shoots lights out and even more consist on paper than the IMR4350. I seem to have good and bad days shooting the IMR, and it really does seem to do with the outside temps.---For sure a batch of Nosler brass using IMR showed more signs of pressure than the 4831 after a couple of reloads.
I've wondered about the R-16 and R-17 and read some good info on them, too. One thing I notice in my old Hornady #9 manual is that their data is different from what Hogdgon publishes on their website. That's a whole other thread. Thanks for all the input.