I'd like to recommend Insurgency Sandstorm for you, as it sits right in the middle of CoD-like shooters and tactical, milsim shooters... but I have myself soured out of it a while ago due to how it's handled by the devs that remained. I did have a fun time with Arma 3, but that required a group to make operations with, and 300GB of disk space for mods. Other kinds of action shooter games that could work are slower paced, vehicle or mech based games, but right now I can't think of a single one that is well maintained and populated.