That's not an adjustment screw 'per se' on your magazine, rather it is a screw which when tightened lets you use .22 shorts in the same magazine that normally uses .22LR cartridges and have them feed correctly.
I beleive that it was the target versions that came equipped with the magazines with that feature & the regular or sporter versions did not have the screw. Either version of the magazines works in any of those rifles. Some got changed around through the years, so may have the wrong one w/them now.
Some of those old Savages are quite accurate; don't overtighten the screws for best accuracy .. roughly 20 inch pounds will suffice. I have enjoyed good < minute of squirrel accuracy using Remington Sub Sonic HP ammo in both a 23A & a 23 Sporter which are similar rifles to yours.
