- Any mass added or removed on the barrel can change harmonics. That may be good or bad, depending on a lot of things.
- Very few of us are using large heavy gas blocks with rails on them. That was a "thing" at one point, but not so much any more except with the bottom end brands IMO.
- Don't mount a plastic folding front sight (like Magpul) on a railed gas block. Heat is a problem.
- Most of the railed gas blocks I've seen have the rail at a different (lower height) than the forend/receiver rail, and don't work for standard folding sights.
TL, DR version - heavy railed gas blocks are kinda dumb and pointless, use something better.
