AR 15 Lower Parts Kits

AR 15 Lower Parts Kits

Familiarizing yourself with the AR15 lower parts kit is essential and integral to every builder’s understanding of their rifle’s internals. You want to build your own AR15 from an 80% lower receiver? Then you need to know how everything fits together. See our AR15 lower parts kit installation guide here for step by step instructions on how to install your LPK the very first time. 

What is an AR15 Lower Parts Kit?

An AR-15 specific lower parts kit is going to be compatible with builds chambered in calibers such as .223 Remington, 5.56 NATO, .300 BLK and other popular cartridges that are compatible with the AR 15 platform.

Lower parts kits include a variety of internal components that go inside the lower receiver of an AR or the frame of a pistol or any gun for that matter. This kit will include everything from the trigger and fire control group, to the springs, detents, safety selector and bolt catch. Usually, installing the lower parts kit is the final step to complete it into a functioning firearm.

What’s in the AR15 Lower Parts Kit? 

Inside the AR 15 lower parts kit you’ll find a variety of parts that turned your stripper lower receiver into a fully functioning firearm. You’ll find the detents and springs for takedown pins which connect the lower receiver to the upper receiver; the detent and spring to install your fire/safe selector switch; detent and spring for the bolt catch lever; spring, threaded backing and magazine release button, a mil-spec trigger and its respective springs and locking pins; the detent and spring which locks in the buffer weight and spring within the buffer tube (which is usually sold separately). Some lower parts kits will come with a pistol grip and buttstock, some won’t for those who already know what furniture they’d rather buy on their own.

How is the AR15 lower parts kit different from an AR-10 lower parts kit?

Many of the parts in both the AR-15 and AR-10 lower parts kits are one and the same. Of the parts that are different and not compatible across the different lower receivers are the following:

  • bolt catch
  • bolt catch roll pin
  • pivot pin
  • takedown pin

For a complete list of all the parts that are and aren’t shared between the AR15 and AR10 parts compatibility, see our blog on that.