I'm still waiting on my first DTI kit (16" Middy) ordered Feb. 27. During the wait I've built my own carbine and I too share the thrill of firing a weapon you've assembled yourself. I built the least expensive rifle I could out of whatever parts I could get my hands on and I tell ya it wasn't easy. All kinds of specialty tools and chasing tiny little detentes and springs around...as Charlie Brown screams "AAAARRRGGGG!!!"
For years I've heard about how inherently accurate the AR platform can be and my very own "Frankenrifle" will consistently put 10 quick Lake City surplus rounds into 2 1/2" Best group at 100 yards so far has been 10 shots within 2" I'm having a hell of a time trying to find small primers to make some of my own loads but they're *#@!* near impossible to find.
Sorry to hear about the failure to hold bolt on empty magazine. I use a PMag 20 round with no window and no problems yet. Might be your hand-loads? Maybe you could ask around the AR-15 page. But be careful over there, they can be testy; testy, but extremely knowledgeable.
As for the horrible DPMS trigger you're in abundant company there.
Now I'm off to see how many hits for Frankenrifle, I'm selling him to a good home to pay for the Del-Ton Middy. I REALLY don't want to but I'm not made of money and I love to build now.
Congrats again on the newborn and safe and happy shooting.