One-piece cantilever mount versus two-piece rings
Why an AR scope usually rides a one-piece cantilever, what the forward offset and 20 MOA cant do, and when two-piece rings are the better choice.
An AR-15 has a long flat-top rail and a short receiver, so a scope needs its rings set forward of the rail slots to reach correct eye relief. A one-piece cantilever mount carries both rings on a single base that reaches forward over the handguard.
Two-piece rings clamp separately anywhere along the rail and are lighter, but on an AR you have to position them far enough forward, which is not always possible on a receiver-only rail. On a bolt gun with the rail over the action, two-piece rings are the norm.
A 20 MOA cant tilts the base forward to hand elevation back to the scope for long range. A QD lever lets the mount come off and go back aiming to return to the same zero, useful for storage or swapping optics.
- ›AR-15 red dot and LPVO mount heightheights
- ›30 mm scope tubecommon LPVO tube
- ›Picatinny rail (MIL-STD-1913)the base cantilevers clamp
Sources: LPVO mounting height guide, Swat Optics · How to select rifle scope rings, Outdoorsmans · 1in, 30mm, 34mm scope tubes and rings, Weaver Mounts