The right-most photo in #19 is a Springfield handguard, not a Remington handguard. The Remington handguard is in the second photo from the left.
Slight manufacturing variation exists in the Remington handguards, but not much. They're reasonably consistent.
I don't know the length of the sight line clearance cut. I don't identify handguards by that feature. Too much variation.
J.B.