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JMT 'Carbon 50' AR-15 80% Gen 2 Polymer Lower w/ Jig & Mil-Spec AR15 Lower Parts Kit (w/ Hammer and Trigger)

Ships Next Business Day


Lighter is Better

The sensible thing is to have the lightest weight possible in your AR build while simultaneously building it with parts that are just as durable as their heavier counterparts. If you can integrate both these qualities into your AR build, then simply put: why the hell not? Now, you can get a lower parts kit with it to jumpstart your next AR build.

James Madison Tactical took one of the lightest AR receivers -- polymer -- and made it even lighter by fabricating the first carbon fiber/polymer hybrid 80% lower. It's super lightweight, yet stronger and more durable than other AR-type polymer 80% lowers. It comes with its own jig too, so all you need is a drill press! The finished receiver will shave those precious ounces off the weight of your workhorse too, so you can have a little more comfort during a long day of shooting.

Polished Lower Parts Kit

Th quality control is second to none and the finish show it: Inside you’ll find a disconnector, hammer hook, and sear that were laser-cut and polished to break as clean as glass at exactly 4.5 pounds. The trigger affords perfect reset after every pull, with no break-in required. Every roll pin presses easily, while the hammer and trigger pins glide in with little effort.

Carbon 50 Polymer 80% Lower Features:

  • Weighs just 4.4 ounces when finished
  • 20% weight reduction over standard AR lowers
  • Stiffer and stronger than many other polymer lowers
  • Mil-spec dimensions make the Carbon 50 fit with all other types of mil-spec parts

Complete AR-15 Lower Parts Kit with Pistol Grip

This AR-15 Lower Parts Kit includes all components required for assembling your AR-15 stripped lower receiver:

  • Bolt Catch
  • Bolt Catch Plunger
  • Bolt Catch Roll Pin
  • Bolt Catch Spring
  • Buffer Retainer
  • Buffer Retainer Spring
  • Disconnector
  • Disconnect Spring
  • Steel Hammer
  • Hammer Pin
  • Hammer Spring
  • Magazine Catch
  • Magazine Catch Button
  • Magazine Catch Spring
  • Pistol Grip (A2 style)
  • Pistol Grip Lock Washer
  • Pistol Grip Screw
  • Pivot Pin
  • Pivot Pin Detent
  • Pivot Pin Detent Spring
  • Selector
  • Selector Detent
  • Selector Detent Spring
  • Takedown Pin
  • Takedown Pin Detent
  • Takedown Pin
  • Detent Spring
  • SSteel Trigger
  • Trigger Guard
  • Trigger Guard Roll Pin
  • Trigger Pin
  • Trigger Spring

Easy-to-Follow Install Instructions

First time assembling, or need assistance with certain steps while installing your lower parts kit? Check out our in-depth instructional and picture guide. It shows the full LPK assembly with tips and tricks, including tools required and the buffer tube and castle nut install.

Need more help or detailed steps? Watch our in-depth instructional video here!

Shipping Restrictions

Shipping of various parts and/or accessories are prohibited to states and locales (ie New Jersey, California, New York, etc…) with restrictions against certain parts and/or accessories or “assault weapons” (i.e. states with high-capacity magazine restrictions, manufacturing of semi-automatic weapons, etc..). It is your responsibility to be aware of your local firearms laws before purchasing from our website or machining a firearm. We try our best to keep our shipping page current, but laws change daily

80-Lower.com only ships within the United States. Federal legislation dictates we cannot ship our products internationally.

We are a national retailer of individual components and not all products depicted on this website are legal in every state. Shipping of various products found on this website are prohibited to some states (such as California, Connecticut, District of Columbia, Hawaii, New Jersey, New York, Rhode Island, and Washington). The information, pictures, text or products presented on this website are not a representation by us, and should not be understood by you, that any product or completed firearm is legal to assemble or own in your state of residence. We encourage each and every builder to perform their own research about the state and federal laws that apply to them. It is your responsibility to understand the law and we encourage you to consult with an attorney or your local ATF representative.