The lack of decent published loads is a problem alright. For a time, I did have a strain gauge instrumented Finn, and collected some data from it. Remember, each rifle is different and military rifles are sometimes especially different from each other. So all this may be completely different in your friend's rifle. My rifle had a 27" barrel, and data were taken with .310 to .311 bullets.
CCI200 primer, Lapua brass, 51 grains Varget, Hornady 123 grain bullet, 2.770" COL, 44.8 KPSI at 85 degree ambient, 3047 FPS. Suggest not going above this.
Czech silvertip surplus, 149 grain bullet, 46.2 KPSI, 2735 FPS.
CCI200 primer, Lapua brass, 50 grains Varget, Speer 150 grain bullet, 2.880" COL, 49.8 KPSI at 85 degrees ambient, 2842 FPS.
S&B commercial 180 grain, 2601 FPS, 58.2 KPSI. Too hot for my tastes. Pulled the bullets and reused the brass.
CCI200 primer. S&B brass, 57 grains H4831 (the old stuff), 174 grain FMJBT, 2.900" COL, 51.6 KPSI at 80 F ambient, 2553 FPS. Really hard to get that much powder under the bullet.
CCI200 primer, S&B brass, 53 grains H4350, 180 grain Sierra bullet, 3.000" COL, 51.0 KPSI at 80 F ambient, 2645 FPS. AA4350 gives nearly identical results.
Hope that helps.