I reload for my 3030's and I have found the 170 bullets to be more accurate. I too have shot sub MOA with my Marlins using 170gr. Speer FP and Nosler PT, though most of the time closer yo 1 1/2 MOA off sand bags. My newest Marlin is a 1975 that I shortened the barrel to 17" and it is my most accurate. I switched from H4895 powder to LeverRevolution powder and never looked back.
tj