The 40x was the base for the M40 series.The M40/A1 used the clip slot whereas the A3/A5 used a "clip Lug". I figure with all the pics out there of a 40X clip slot, next to regular 700 actions, you could translate the dimensions. The M40/A1 slots were cut by Marine armorers, but the 40X is a Remington factory thing.