I'd load up a heavier grain bullet for the 1:8 Twist, will get a higher BC and more knock down power at longer ranges. When I first started shooting RUM's, Hornady had released Factory 220gr ELD-X and it shot well out of a 26" 1:10 twist…however, the 200gr ELD-X performed much better (side note, these were hand-loads 89gr-93gr Retumbo/Fed 215M/Hornady Brass/ COAL 3.625..with no pressure and well below max powder). Was averaging 3/8"-5/8" pending my performance as a shooter. Tried the Barnes LRX in 200gr with all of the above load info & my rifle liked the ELD-X (most likely due to cup & core vs. monolithic style of bullet). Have not shot the Hammer, IMO there are better options on the market. I like the Hornady, Berger & Barnes, this all based off of real life experiences & usage on game.
Hope this helps, feel free to PM me for more info…RUM MAN is a wealth of knowledge on this, he would be the go to if I had questions.