That is one great looking rifle, makes me really miss mine as it was the same classis rilfe style. I used RL22 with 220 hornady and 200 tsx with great accuracy.
No experience with the 8mm mag, just 8x68S
I had good results with 200gr Accubonds in front of mrp.
With the next lot of powder, it looked similar to your results. Couldn't make them fly...
Changed to N160, which isn't perfect but was standing around from another project, groups were fine again and power is ok.
So - maybe your gun simply does not like that powder?
Good looking rifle. I know someone has already asked about how far off the lands are you loading. When I first saw the picture of your loaded rounds I said to myself those look like their loaded really deep into the case. My want to try seating depth change. The 200 AccuBond should make a GREAT bullet for this rifle because it will hold together even on close shots. I push the 130 AB in my 264 Win mag 3350 fps and even on a deer at 25 yards it stays together and exits with about the same terminal results as it does at 500 yards. Retumbo powder might also work well, it makes my 264 mag sing.