One Horse 18" Complete Upper 6mm ARC 1:7.5" Twist

The One Horse 18" Complete Upper is a complete AR-15 upper receiver kit chambered in 6mm ARC, built around an 18" barrel with a 1:7.5" twist rate. The 6mm ARC caliber offers excellent long-range performance with superior ballistic coefficients compared to traditional 5.56 NATO. The 18" barrel length provides optimal velocity for this precision cartridge, making it ideal for long-range shooting and hunting applications. This complete upper assembly is ready to install on any mil-spec AR-15 lower receiver.