30mm barrel with 60mm bell:
1.35" high rings (35mm) put the bell +5mm above the mounting rail (weaver or picatinny).
1.20" high rings (30mm) put the bell 0mm above the mounting rail (weaver or picatinny).
1.00" high rings (25mm) put the bell -5mm above (5mm below) the mounting rail (weaver or picatinny).
0.8" high rings (20mm) put the bell -10mm above (10mm below) the mounting rail (weaver or picatinny).
56mm bell adds +2mm to the above calculations. I bought 1" high rings for my scope with 30mm barrel, 56mm bell. My mount is a 10mm high pincatinny rail on a varmint profile barrel so I could have gone with the 0.8" but I was chicken. [/QUOTE]