I had a fair share of lower quality AR's before getting rid of them to switch to quality brands. In the AR world, there are manufacters who make quality guns, and those that don't. Some skimp on important processes that make guns reliable and long-lasting, while others don't.
Your typical "consumer" brands like Del-ton, Rock River Arms, Bushmaster, DPMS, Olympic, Stag, ect, are those kinds of manufacturer.
If you want a DECENT weapon, like I said, sell your Del-ton upper and buy a upper from a manufacturer that DOES do the right things, like BCM, Daniel Defense, ect.
Look, heres what I would do if I were you. Keep the lower you have now, its probably decent. Sell your Delton upper and BCG on Gunbroker or on AR15.COM's Equipment Exchange. Get some money back from that original purchase. Then save up some extra cash, and buy this:
http://www.bravocompanyusa.com/BCM-M...-urg-m4-16.htm
And you will need a quality BCG to go with it:
http://www.bravocompanyusa.com/BCM-B...0auto%20mp.htm
I would also read up on these threads:
https://www.m4carbine.net/showthread.php?t=56063
https://www.m4carbine.net/showthread.php?t=6642
https://www.m4carbine.net/showthread.php?t=7376
I may be coming off as harsh, but trust me, I am doing my best to help you and point you in the right direction. ;)