two
I've used a set of Leupold QRL rings on an early Savage 10C Scout in .308 for at least 20 years. Return to zero is not always absolute, but always within 1 MOA. The IER set up is for a Leupold 2.75x a scout scope. In the past 5 yrs or so, I acquired a Burris 2-7x scoutscope and Warne QR lever rings and have noted the same performance as the Leupolds. Return to zero is within 1 MOA or less. I use the two QR set ups on the same old Savage 10C .308 Scout.
Note I do not mount/dismount the scopes on a daily basis or dork with them back and forth for grins. I run the 2.75X about 75% of the time for GP use, and utilize the 2-7x variable a bit if I hunt the rifle on whitetails. I've shot/dismounted and remounted/ shot the rigs in testing that I have no qualms about swapping scopes and taking a shot on whitetails or some type of threat, but do not claim the arrangement as a precision rig, but a practical arrangement for two different reticles and a spare scope on hand (well, nearby anyhow) if needed.