I change my AR's around so much, it is hard to remember what I have and what works...
The one thing I would never change is the Timey trigger drop-in system...It is great. I have mine set at 1pound 8 ounces...It is smooth as glass...More than a few have tried it, and all will agree...It is worth the money..
I have a Spikes flattop upper on one of my AR's..I like it...I wish now that I would have had the painting done on it...
I have a Colt heavy barrel on one of mine. It is nice, but, sure is heavy. It has had a M-16 full up lower on it, and I ran about 400 rounds thru it one day...And, it still shoots straight...
I hope my rambling helps....It you want to try my AR's, just to see the differences, just let me know and we will go shooting...
Being retired does have some perks.....
Steve