8x56,
If you don't have time to work up these loads then you best bet by far is to zero your gun with solids and forget the softs..

I believe the smaller the caliber the more you need solids for Buffalo...in fact when I hunt Buff with 9.3s or the 375 I only use solids...With 416 and up I may have a soft or two around. I have never seen a solid fail, I have seen many softs fail to one degree or another.