I need to be educated about gas blocks. I'm building an AR15 SBR with BCM 11.5 inch barrel. My plan is for a 9 inch DD Lite rail so I need to install a low profile gas block.

My confusion revolves around set screw vs pinned vs clamp-on ( or any combination thereof). Is pinning the gas block preferable? Mandatory? The BCM barrel has one dimple, do I need to have Addco or somebody add the second dimple then pin the gas block? I've heard horror stories about people trying to unpin Noveske gas blocks to install their barrels - is this a universal experience with all manufacturers?

And, in what order do these installations occur? I have to get the barrel nut on, so do I install the barrel and rail mount ring to the upper receiver first, then send the barrel/receiver to get the gas block pinned, then install the rail when I get it back?

Rudimentary, I'm sure. Thank you for your patience.