I have a terrific Shilen action in 22 PPC (1-8") Bartlein.  It shoots 69 sierras at 200 really well but I am trying to make loads for 77-80 Sierra
And Berger 80's.  I am using Varget at 23.5 to 25.0 and not finding the sweet spot. (Pressure signs - flat primers at 25.0)

I was hoping to shoot this rifle in NRA mid-range matches ( 600 yes).

German has an old article on this.  I wondered if anyone else had experience here

I have been shooting 223 @ 600 yards with the 77 gr TMK with good results. With a G1 BC of 0.420 it can run with the 80s. I wouldn't  bother with the 77 SMK for 600 when there are other choices with much higher BCs.

Bullets to consider:
75 and 80 gr AMAX
80.5 Berger fullbore
One of the Berger VLDs 75/80

Lots of info on other forums, google can show the way.