One Horse AR-15 Lower Parts Kit

Complete Mil-Spec LPK - Made in America The One Horse AR-15 Lower Parts Kit provides every pin, spring, detent, and component needed to complete a fully functional AR-15 lower receiver. This comprehensive Mil-Spec kit includes everything except buffer tube assembly and stock, making it ideal for finishing stripped lowers or replacing worn components. The phosphate-coated single-stage trigger delivers crisp, reliable 5.5–7 lb pull with proven Mil-Spec geometry. All parts are precision-machined for drop-in compatibility with any Mil-Spec AR-15 lower receiver. Made in America with U.S.-sourced materials, U.S. manufacturing, and strict quality control at every step. No shortcuts, no imported parts—just dependable components built by craftsmen who take pride in American manufacturing.

Complete Lower Parts Kit

This comprehensive kit includes every component required to build a complete AR-15 lower receiver: single-stage Mil-Spec trigger, trigger spring, hammer, hammer spring, disconnector, disconnector spring, trigger pin, hammer pin, selector, selector detent, selector detent spring, bolt catch, bolt catch plunger, bolt catch spring, bolt catch roll pin, magazine catch, magazine catch button, magazine catch spring, takedown pin, pivot pin, takedown/pivot detents (2), takedown/pivot detent springs (2), buffer retainer, buffer retainer spring, trigger guard, trigger guard roll pin, bolt release roll pin, A2-style pistol grip, pistol grip screw, and pistol grip lock washer. The only components not included are buffer tube assembly and stock, which are typically selected based on specific build requirements.

Mil-Spec Single-Stage Trigger

The single-stage Mil-Spec trigger features proven military specification geometry delivering crisp, reliable 5.5–7 lb pull weight. The phosphate coating provides corrosion resistance and reduced friction for consistent trigger operation. Single-stage design offers straightforward, predictable pull characteristics familiar to shooters experienced with standard AR-15 triggers. The trigger, hammer, disconnector, and springs work together as a complete fire control group engineered for reliable ignition.

Phosphate Coating

The phosphate coating on the trigger and hammer provides corrosion resistance while reducing friction between moving surfaces. This finish treatment extends component life and ensures smooth, consistent operation even in adverse conditions. The coating maintains its protective properties through thousands of trigger pulls.

Precision-Machined for Drop-In Compatibility

All components are precision-machined to Mil-Spec dimensions ensuring drop-in compatibility with any Mil-Spec AR-15 lower receiver. The tight tolerances eliminate fitment issues during assembly while maintaining proper function. Parts install without modification, fitting, or adjustment required.

Complete Fire Control Group

The fire control group includes trigger, hammer, disconnector, and all associated springs and pins. These components work together to provide reliable firing mechanism function. The Mil-Spec geometry ensures compatibility with standard AR-15 upper receivers and bolt carrier groups.

Selector and Safety Components

The selector (safety) with detent and detent spring provides positive engagement in safe and fire positions. The selector rotates with tactile and audible clicks, indicating proper engagement. The detent and spring maintain selector position during use and prevent inadvertent safety disengagement.

Bolt Catch Assembly

The bolt catch assembly includes bolt catch lever, plunger, spring, and roll pin. This complete assembly enables last-round bolt hold-open function when used with appropriate magazines and provides manual bolt hold-open capability. The bolt catch interfaces with the magazine follower to lock the bolt carrier rearward when the magazine is empty.

Magazine Catch Assembly

The magazine catch assembly includes magazine catch body, magazine release button, and spring. This threaded assembly enables secure magazine retention with quick, positive magazine release. The button is accessible from the firing-hand side for rapid magazine changes.

Takedown and Pivot Pins

The takedown and pivot pins with detents and springs enable separation of upper and lower receivers for cleaning, maintenance, and transport. The detent-retained design holds pins in place during normal use while allowing intentional removal for disassembly. The spring tension keeps pins securely seated.

Trigger Guard

The included trigger guard with roll pin protects the trigger from inadvertent contact and provides a mounting point for the lower receiver's front section. The trigger guard accommodates gloved or bare-handed shooting.

A2-Style Pistol Grip

The A2-style pistol grip provides comfortable, ergonomic purchase with traditional AR-15 geometry. Included grip screw and lock washer secure the grip to the lower receiver while retaining the safety selector detent spring. The A2 grip features storage compartment for small items or spare parts.

Made in America with Uncompromising Standards

Every One Horse component is manufactured in America using U.S.-sourced materials and U.S. manufacturing facilities. Strict quality control at every production step ensures consistent quality and reliability. No shortcuts, no imported components—just dependable parts built by people who take pride in American craftsmanship. The One Horse AR-15 Lower Parts Kit delivers everything needed to complete a Mil-Spec lower receiver—quality American-made components you can trust every day.

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SPECIFICATIONS

• Manufacturer: One Horse
• Model: AR-15 Lower Parts Kit
• Type: Complete Lower Parts Kit (minus buffer tube assembly and stock)
• Platform: AR-15 / Mil-Spec Lower Receivers
• Trigger Type: Single-Stage Mil-Spec
• Trigger Pull Weight: 5.5–7 lbs
• Trigger Finish: Phosphate Coated
• Standards: Mil-Spec (Military Specification)
• Compatibility: Drop-in with any Mil-Spec AR-15 lower receiver
• Country of Origin: Made in USA
• Materials: U.S.-sourced
• Manufacturing: U.S. facilities
• Kit Includes:
• - Single-stage Mil-Spec trigger
• - Trigger spring
• - Hammer
• - Hammer spring
• - Disconnector
• - Disconnector spring
• - Trigger pin
• - Hammer pin
• - Selector (safety)
• - Selector detent
• - Selector detent spring
• - Bolt catch
• - Bolt catch plunger
• - Bolt catch spring
• - Bolt catch roll pin
• - Magazine catch
• - Magazine catch button
• - Magazine catch spring
• - Takedown pin
• - Pivot pin
• - Takedown/pivot detents (2)
• - Takedown/pivot detent springs (2)
• - Buffer retainer
• - Buffer retainer spring
• - Trigger guard
• - Trigger guard roll pin
• - Bolt release roll pin
• - A2-style pistol grip
• - Pistol grip screw
• - Pistol grip lock washer
• Not Included: Buffer tube assembly, stock