Is the disconnecter spring installed upside down? (larger portion of spring needs to be facing down)?
eta- you did this correct?
––-INSPECTION OF LOWER
-Trigger guard should not protrude into the magazine well.
-Insert a magazine into the magazine well and ensure that it drops free.
-Check the pivot pin, and takedown pin for wear and fit, they should be snug but slide easily.
-Check disconnector engagement: with the trigger forward, rotate the hammer to just short of the cocked position; the tip of the disconnector should almost touch the middle hammer hook. Holding the trigger to the rear, cock the hammer and release the trigger, the trigger should catch the hammer, and the hammer should smoothly slide out from under the disconnector hook.
-Do not allow the hammer to strike the lower receiver or the bolt catch.
-Remove the hammer and check the hammer spring for proper placement and tension. Inspect the middle hammer hook, lower hammer hook, and the “J” spring for damage. Ensure that stake retaining the “J” spring is present.
-Remove the trigger and disconnector. Check for proper installation of the trigger spring and that the disconnector spring is present.
-Check the hook of the disconnector for damage.
-Inspect the trigger, check the tension of the trigger and disconnector spring, and look for wear or damage on the sear face of trigger.
-Ensure that the disconnector slides easily in the trigger slot.
-Check the inside of the lower for foreign matter, such as a primer in the pistol grip hole.
-Remove the buffer and spring and inspect them for damage; such as small indents in the face of the buffer caused by the buffer retaining pin. Check the buffer spring for proper length; 11 ¾”-13 ½” for rifles 10 1/16”-11 ¼” for carbines.
-Check the buffer retaining pin for function and range of motion.
-Check the buttstock screws and lower receiver extension for tightness.
-Reinstall the buffer and spring.
-Reinstall the trigger, disconnector, and hammer.
-When installing the hammer the hammer spring legs must be on top of the trigger pin and in the outside annular groove on the trigger pin. Failure to do so will allow the trigger pin to move. The wide end of the disconnector spring goes into the hole in the trigger.