Most No. 4 based target rifles like this were set up and intended to be used with 7.62 ball ammunition.
If this one has the Palma chamber, then I assume that it has had a barrel recently fitted for .308.
Or, could it possibly have had its 7.62 chamber recut with the Palma reamer?
If it was a 7.62 shooter, there is a pretty good chance that it is tight bored, another possible complication.
I agree that 46.5 of Varget with a jammed bullet would not be a good idea.
Start lower, work up.
Something else - if you are on the range and it rains, keep the action and your ammunition dry.