Researching A1 / C7 Upper's

Hi all,

Regardless of how modular the AR15 is, it's the A1/C7 that I fell in love with. While I don't plan on buying or building an A1/C7 anytime soon, I like to do my research as I have learned there are some things that are just a tad different from what I know. Anyone able to help me understand?

• If I was gonna buy a complete upper receiver, are there any particular manufacturers that I should look at first or who to avoid?
  • BKF
    • This model seems like it has all the modern updates which is something I would like to have.
    • https://bkingsfirearms.com/shop/complete-upper-receivers/bkf-m16a1-20-5-56-pencil-profile-rifle-length-w-fsb-complete-upper/
  • PSA / H&R
  • TNTE
  • JSE Surplus
• I read that there is a difference with the A1 and the C7 Carry Handle? As in the A1 doesn't have the option to mount options but the C7 does?
• How necessary are M4 feed ramps? From what I understand, the carbine length gas system had feeding issues that necessitated the M4 feed ramps but I would assume with a rifle length gas system it "shouldn't" have this issue?
• F vs non-F FSB? I think one of them is meant for flat-top receivers?
• Anything else I should know?