I had one of those over a decade back and it was quite accurate with flat base, round nose bullets, with exposed lead bases.
I know in this day and age such bullets are frowned on. I know it's easier to build accurate bullets from the base up but exposed lead bases had some very good advantages, when considering the varying bore diameters of days gone by.
Likely the first thing you should do, is slug the bore on your particular rifle.
These rifles are fairly strong and can handle loads producing slightly over 40K PSI.
My go to load for the rifle was Norma 196 grn RNFB over 46 grains of IMR 4895 with CCI 250 primers. The cases were made by Bertram.
This load was safe in my rifle.
Some of those old Danish Rolling Block rifles had strength issues. I believe, all of them were made in Sweden, some were converted from the original 50-70 case and the last ones were purpose built originally for the 8x58R D cartridge, which they also used in Krag repeating bolt action rifles.
There is actually a lot of information on your rifle type on the internet, along with all sorts of loads and how to get them to shoot well. My biggest problem was finding brass.
My rifle wouldn't shoot light 150 grain bullets well. It was OK with cast lead but not great.