Geissele MK16 Super Modular Rail 13.5" (URGI)

The Geissele MK16 Super Modular Rail in the 13.5-inch length is the handguard that defines the URGI. USASOC adopted this exact rail (NSN 1005-01-672-4797) for the Upper Receiver Group - Improved program, replacing the Daniel Defense RIS II quad rail of the SOPMOD Block II era. Precision machined from 7000-series aluminum with Type-3 hardcoat anodizing, it pairs the updated Geissele barrel nut with a full-length M1913 Picatinny top rail and M-LOK on seven sides.

The 13.5-inch length is the canonical URGI dimension, sized for the 14.5-inch cold hammer forged government-profile barrel that the program runs. Unlike Geissele's Super Duty line with its proprietary dovetail fittings, the MK16 mounts to standard forged upper receivers, so it drops into a parts-built URGI upper without a proprietary upper. Anti-rotation tabs and set screws hold zero under sustained suppressed fire.

If you are building a strict URGI clone from components rather than buying a complete Geissele upper, this is the single part that establishes the silhouette. Pair it with the 14.5-inch CHF barrel, a low-profile gas block, and a pinned SureFire muzzle device to reach the issued configuration.