Old guy here...I started with Colt AR15A2 HBAR..as I got older and my eyes starting getting older with the rest of my bones I could no longer shoot the carry handle mounted scope set up well. Bought a RR Varmint EOP for PDs and that killed my Colt days..gave it tio my son. He has YOUNG eyes, muskels and so forth so good to go.
Like an earlier poster I had to use pliers, well LockGrips, to tighten the base so it stay..I did not like that,,seemed like a "Get a BIGGER hammer" solution to me.
I did swap out a CAR15 upper for a EOP..was failry cheap, caught on sale - $70-$80..probably DPMS. I'm completely out of the carry handle business.