Didn't try to find it but Craig Boddington was one of the few writers that championed the 8mm RM. He reviewed the rifle and cartridge in 1978 for guns & ammo I believe and chronoed factory and some handloads then. He had a heavy rifle built by I believe Prairie Gun works with a 28" barrel if memory serves. He was trying to get the 200 & 220s over 3,000 fps which his handloads did in that rifle.

I wouldn't be too concerned on the velocity of factory loads as it won't be lacking even if under advertised specifications. The Heavier core lokt is a good bullet but I would consider something even stouter if possible. I always wanted to try the 250 Woodleigh in the big 8. This would turn it into a sort of modern 318 Westly Richards and should be good for anything short of Tyranosaurs.

"When you disarm the people, you commence to offend them and show that you distrust them either through cowardice or lack of confidence, and both of these opinions generate hatred." Niccolo Machiavelli