The Arisaka Zero Retention Clamp (ZRC) (brand part no. ZRC-SPEAR-LT) solves a specific problem on the SIG MCX Virtus and Spear LT platforms: their factory handguards are not adequately secured to the upper receiver, letting the handguard flex enough under hand pressure to shift a laser or iron sight’s zero by 5 mils or more, and that zero doesn’t always return once the pressure is released. This version fits the MCX Virtus in 5.56 and .300 Blackout, and the Spear LT in 5.56, 7.62×39, and .300 Blackout (the Rattler is not currently supported). Exterior clamps thread into a special U-bracket that engages the extended upper receiver underneath the handguard, securing it tightly across two axes without touching the barrel or gas system, so the barrel stays free-floated. Clamps are contoured to minimize interference with the shooter’s grip on the handguard.

Key Specifications

• Fits the MCX Virtus in 5.56 and .300 Blackout.
• Fits the Spear LT in 5.56, 7.62×39, and .300 Blackout.
• Rattler is not currently supported.
• Secures the handguard to the receiver across two axes, reducing zero shift.
• Uses a U-bracket that engages the extended upper receiver.
• Does not touch the barrel or gas system, preserving the free float.
• Clamps are contoured to minimize interference with the shooter’s grip.

Frequently Asked Questions

What problem does this clamp solve? Factory MCX Virtus and Spear LT handguards can flex enough under hand pressure to shift a mounted laser or iron sight’s zero by 5 mils or more.

Does the clamp touch the barrel? No, the U-bracket engages the extended upper receiver, not the barrel or gas system, so the barrel stays free-floated.

Does this fit the Rattler? No, the Rattler is not currently supported by this clamp.

Buy the Arisaka Zero Retention Clamp for MCX Virtus and Spear LT

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