UHPR-15.0 MOD 3 HDX Quad Rail

The UHPR-15.0 MOD 3 HDX Quad Rail is a free-float HDX MOD 3 handguard machined from billet aluminum and finished in black Type III hardcoat. It carries a continuous MIL-STD-1913 top rail that indexes flush with a flat-top upper, and MIL-STD-1913 rail on all four sides.

CMT's barrel nut does not have to be timed. There is no shim stack to chase and no clocking the nut to clear the gas tube — torque the nut, slide the rail on, and clamp it. That removes the single most common source of a canted rail and lets the same nut come back off for barrel work without a fight.

Fitment

• Mil-spec AR-15 flat-top upper receiver
• Intended for a 16–18 in. barrel running a mid-length or rifle-length gas system
• Clears low-profile gas blocks up to .750 in. journal diameter
• Will not clear a standard A2 front sight base or a clamp-on gas block with an oversized body

In the box

• UHPR-15.0 MOD 3 HDX Quad Rail
• CMT barrel nut
• Clamp hardware and wrench flats sized for a standard armorer's wrench

Installation. Fit and torque the barrel nut to the value in the instructions with the upper in a proper vise block and reaction rod. Confirm the gas tube passes through the nut without contact before clamping the rail, and verify gas-block alignment before the first live round. If you are not equipped to torque a barrel nut, have a qualified gunsmith install it.