Good luck and hope you find your problem, which seems to correspond with the Springs and their Leg positions. Also when done don't forget a good amount of OIL in the Trigger Group to keep things limbered up.
Also, being New to AR's, DO NOT Dry Fire the Rifle without the Upper attached, OR your Finger in front of Hammer to keep from breaking/cracking the Cross Rib of the Lower that the Hammer will slam up against when you pull the Trigger for testing. You might get by with one time of this mistake, but the 2nd time could destroy the Lower.
Myself, I wouldn't Dry Fire even if the Upper was installed without some Hammer protection for it to slam up against---like some thick Rubber, soft Plastic, Leather, but that's just me. Metal on Metal just tells me things just won't go right.