168 SMK's are ok out to 800 yards, might still be ok at 900 but are right crap at 1000 yards. These bullets were designed in the 60's for 300m ISU shooting. I have used them for 300 yard ISU matches but find they are no better than 155 SMK's at that range.
I have always liked the 155 Sierra old style Palma bullets but the new 155C Palma's are even better. 155 Noslers work well if you can get them. Lapua 154 Scenars are a great bullet as well as 155 Berger VLD's.
I tried 155 AMax bullets when they first hit the market (old style) and could not get them to shoot. Tried some last year and I will say they are about the best bullet I have shot at 300m. I have not tried them at long range but will pick up more of them for short range only.