Can you provide any info the brand of lower receiver, and trigger group? It sounds like you either have a badly machined receiver where the hammer & trigger pin holes are located out of spec, or you have bad hammer and/or trigger sear engagement surfaces.
If the gun fires on the release of the trigger, then it sounds like a bad hammer to trigger sear engagement, and not the disconnector. After you press the trigger, and the hammer goes forward striking the firing pin and the ammo fires, if you keep the trigger pressed to the rear as the hammer recocks, the hammer will be caught/captured by the disconnector, and stay there as long as you keep the trigger pressed rearward. When you release the trigger so it can go back forward, the hammer should release from the disconnector and return to the hammer to trigger sear engagement.
Here is a function test that we teach in armorer courses:
1. Cock the Hammer and put the Safety into the "Safe" position. Try pressing the trigger, nothing should happen, as this tells you the Safety is working correctly.
2. Put the Safety into the "Semi" position. Try pressing trigger, and the Hammer should release from the Trigger and Fire. Now let go of the Trigger, and manually cycle the Charging Handle rearward, which should now recock the Hammer rearward so it engages the Trigger (Hammer to Trigger Sear Engagement). Try pressing the Trigger again, and the Hammer should release like before and fire. Repeat 3-4 times to ensure.
3. Pull the Charging Handle rearward to manually cycle the action so the Hammer cocks and is caught by the Trigger (Hammer to Trigger Sear Engagement). Press the Trigger so the Hammer releases and fires. Now press the Trigger rearward and hold it to the rear while you manually cycle the action by pulling the Charging Handle, which should recock the Hammer so it should be captured by the Disconnector. Slowly release the Trigger, and you should feel & hear a soft clunk type sound, which is the Hammer releasing from the Disconnector, and the Hammer should now have gone forward and be caught by the Trigger (Resulting in Hammer to Trigger Sear Engagement), then press the Trigger again so that Hammer goes forward and fires. Repeat 3-4 times.
CY6
Greg Sullivan "Sully"
SLR15 Rifles
TheDefensiveEdge.com
(763) 712-0123