I am using the 250 grain Barnes TTSX with 74 grains of Vihtavuori N150 and get great accuracy(3 shot groups between 1/2" and 1"). I have not checked the velocity of it yet.
I had to stop at 74 grains because I had no more space in the case because I had to set the bullet so deep. No signs of me getting close to max loads with that in my gun.
I plan to check the speed this summer.
And I also plan to try Vihtavuori N140 next to see how that will do.
I am also using some 300 grains round nose soft points from Partizan with 72 grains of Vihtavuori N150 that gives me about 1" groups with no pressure signs.
I have not tried to load it up more and I don't care about the speed, as I just use it for target practice because it is the cheapest .375 bullet I have managed to buy here in Norway.