Maybe a PM to Mule Deer as I am pretty sure he shoots a similar gun so chambered.
John shoots an 8X57JRS in a drilling that's pretty accurate. He could give some good 1st hand loading advice, since the rounds are so similar.
After looking at the photo I think you have a very sweet gun there. It's older and not as stout as the post war guns, so stick to the conservative JR loads.
It looks like you don't have it scoped, so slow the lighter 175-180gr bullets down; not as fast as the 196gr factory fodder. If you run them out as fast or faster you will most likely shoot way low to the iron sights. Try a couple of the 175s at 2,275 fps, and see where they print. Shoot two, then cool the gun down a lot, then shoot two more. If they shoot low slow them more or go to the 96-200gr bullets. They'll climb as the rifle barrel warms up, so shoot a cold gun to sight in and work up loads. Break the gun down to hasten cooling. It's also good to shoot the gun 3-4-5 or more times in fast succession and record where each prints as the gun warms.
Combo guns take getting used to and patience. IMO you have a good one.
