The smallest I'm aware of (on a currently available new scope) is 1.360 on the Leupold 3-9 Freedom A.O. EFR.*
What type of rings/bases does the gun have? Many of these had the claw mounts. Probably the cleanest setup I've seen was an offset mount that moved the scope a bit to the left to clear the 'butter knife' bolt handle. -Al
*Heck of a nice little scope
