The factory Tikka rings have plenty of clearance for the Burris FFII 3-9x40 atop my T3. A 44mm would fit, and a 40AO probably would, too. For a hunting .223, I would recommend the Burris like mine, 3-9x, with Ballistic Plex. If you are doing varmint work, look at a 4-12x40 with parallax adjustment. I would try a Swift, Mueller or EABCO, all of them very reasonably priced and slim.