A fiber optic connector is disclosed that includes a plug body having a plug end and a connector core that mounts within the plug body. The connector core includes a ferrule subassembly including a ferrule, a ferrule hub that attaches to the ferrule, a spring holder and a connector spring. The ferrule sub-assembly is assembled with the connector spring pre-compressed to an initial compressed state prior to mounting the connector core within the connector body. The plug body and the core are configured such that the connector spring is moved from the initial compressed state to a final compressed state when the connector core is loaded in the plug body. In certain examples, tuning features can be integrated into the connector core.