Looking for load data on 30cal 155.5 fullbore berger. 20" barrel 1/10 twist. I emailed berger never got a response. I have used benchmark up to 44.5 grains lapua brass federal 210 primers. Seating is .020 off lands.
. For your 155 5 and 20 inch barrel.
46 to 46.4 of Varget will get you 2880 .same load with a 30" would be 3050.
Sierra,2156 with the same stuffing is also a good load.
There is also a sticky for 308 Service Rifle loads and many load data sites also make a special section for those versus longer bolt gun loads.
You may want to study both sections since you are mixing a Palma bullet which is normally shot in a longer barrel, with a 20" which is more in line with service rifle sling shooting where 168 - 175 is more common. That said, there is nothing wrong with using a Berger or Sierra Palma bullet in a 20" barrel if your rig likes it.
You will find a recurring theme with Varget, N140, and some others, showing up over and over. Do yourself a favor and try those first.
If your rig doesn't shoot with Varget or N140 with a Palma bullet, then try a 175 grain match bullet or a 168/169 grain match bullet and see if that works better.