Like Virginia7 said whatever shoots best in your rifle. My Win Model 94 loves 170 grain Core-lokts, but hates most 150 grains, especially ones from Winchester. If your friend had it shooting that well with the 150 grain super-xs than maybe that is what you should use. After the season try a few diffrent rounds and see what you like best. One of the great things about the 30-30 is that ammo is pretty cheap and plentiful so it wont break the bank to try diffrent ones.