Smith & Wesson M&P AR-15 Customizable Lower Parts Kit - Complete Kit (Excludes Grip)

Building a custom AR-15 from the ground up gives you control over every detail—and the Smith & Wesson M&P AR-15 Customizable Lower Parts Kit makes sourcing the internal components straightforward. This complete kit supplies all the small but critical parts that go into the lower receiver, so you can focus your budget and attention on the upgrades that matter most to your build. Whether you're assembling your first rifle or your fifth, having a reliable baseline parts kit saves time and eliminates the guesswork of tracking down individual springs, pins, and detents across multiple suppliers.

The kit is intentionally designed with customization in mind. By excluding the grip, it leaves that choice entirely to you—critical for shooters who have strong preferences about ergonomics, angle, or material. The same philosophy applies to other popular aftermarket upgrades; the kit provides the foundation while you add the components that match your shooting style, mission, and budget.

These are genuine Smith & Wesson parts engineered to M&P specifications, so fit and function are proven. For AR-15 builders who want quality baseline components without paying for unnecessary proprietary upgrades, or who plan to spec out a rifle with specific aftermarket triggers, grips, or other custom pieces, this kit delivers exactly what you need—nothing more, nothing less.

What's Included

• Bolt catch assembly (catch, plunger, and roll pin)
• Buffer retainer and spring
• Hammer pin
• Magazine catch assembly (catch button and spring)
• Pivot pin assembly (pin, detent, and spring)
• Selector assembly (selector, detent, and detent spring)
• Takedown pin assembly (pin, detent, and detent spring)
• Trigger pin

Specifications

Frequently Asked Questions

Will this kit work with my AR-15 lower receiver?

Yes—these are M&P-spec parts engineered for AR-15 lower receivers. They are compatible with standard AR-15 platform builds.

What's not included, and why?

The grip is excluded to give you full freedom to choose the ergonomics, angle, and material that suit your hand and your rifle's mission. The kit contains all the internal springs, pins, catches, and detents needed for the lower to function.

Is this kit suitable for a first-time AR-15 builder?

Yes. If you're new to AR builds, this kit removes the complexity of sourcing dozens of tiny parts individually. You'll still need to source or provide a lower receiver, upper assembly, and grip separately, but the kit gives you a solid, complete baseline to build from.

Can I use aftermarket triggers and selectors with this kit?

The kit includes a standard selector and trigger pin. Many builders use this as a baseline and upgrade to custom triggers or selectors later; compatibility depends on the specific aftermarket part you choose, so verify fitment with the manufacturer of any upgrade.