I have several rifles chambered in 30-30. Some shoot better groups with 150 grain factory ammo and some do better with 170 grain factory ammo. The 30-30 rifle that I was shooting last year shot good groups with Winchester/Olin 150 grain Deer Season XP factory ammo, but not enough better than any of the 150 grain soft-points from FED/REM/WIN to chose them if the difference in price was important to the shooter.
I have a Savage 170 that shoots its best groups with the Hornady 160 grain LeverEvolution, while another Savage 170 does better with Remington 170 grain RNCLs. I shot FED/REM/WIN 170 grain factory ammo in a Marlin 336 and all of them would shoot around 2.5 MOA interchangeable. No single brand shot enough better than another brand, so I bought whatever brand was less expensive at the time.
Try a couple different brands and bullet weights.
