Re: 7mm ultra mag
Mikael, like Dave said, start with lower powder charges & work toward maximums slowly, as pressure DOES peak suddenly with most powders in this caliber.
With heavier bullets (+160gr), a powder suitable for a 50BMG might be in order. Mine likes 5010 surplus powder better than anything. Since you're a Scandanavian, Vihtavouri makes some good ones that could be the ticket. I've been curious about 20N29 & one other one I can't remember at the moment. Something on the burn chart around Retumbo/ H1000/ 5010 should get you close. Best of luck.