Well you’ve done it – you’ve purchased your Aero Precision stripped lower receiver for your AR build and you’re determined to build your AR15 from scratch. You might wonder, what parts are needed to build a lower receiver? That’s where the Aero Precision lower parts kit comes in.

Use this article as your guide to purchasing the parts needed to build your lower receiver.


Aero Precision Lower Parts Kit

There are many versions of the AR15 lower parts kit (LPK). See below for which one best suits you. 

This guide is best specific to the AR-15. You’ll find similar parts for an AR-10 and Aero Precision EPC-9 build but some parts may be hardened, more durable, or a different size due to the receiver size and specifications.

Complete LPK

These kits contain a fire control group (aka FCG), pins, springs, and pieces necessary to make your lower receiver operational. Here’s a complete list:

  • Pistol Grip
  • Takedown Pin
  • Detent Pivot Pin
  • Takedown/Pivot Detent
  • Takedown/Pivot Spring
  • Bolt Catch
  • Bolt Catch Buffer
  • Bolt Catch Roll Pin
  • Bolt Catch Spring
  • Magazine Catch Body
  • Magazine Catch Button
  • Magazine Catch Spring
  • Buffer Retainer
  • Buffer Retainer Spring
  • Safety Selector Switch
  • Safety Selector Spring
  • Safety Selector Detent
  • 4-40 Set Screw (for threaded takedown pin detent hole)
  • Trigger (with trigger pins)
  • New Hammer
  • Trigger Spring
  • Trigger/Hammer Pins
  • Hammer Spring
  • Disconnector
  • Disconnector Spring

You can find just about any version of grip in these. The Aero Precision M4E1 MOE SL Lower Parts Kit contains a MAGPUL MOE SL grip in it. 


See below if you want to customize even further.

Aero Precision Lower parts kits [minus FCG/trigger assembly]

This kit contains all of the parts from the complete lower parts kits except:

  • Trigger/hammer pin
  • Trigger spring
  • Hammer spring
  • Disconnector spring
  • Hammer
  • Trigger
  • Disconnector

This is a great kit for someone who wants to install an aftermarket trigger, like a CMC trigger.

Aero Precision Lower parts kit [minus FCG/trigger guard/pistol grip]

Just as it sounds, this is an AR15 kit without the FCG, trigger guard, and grip. If you plan to use a specialized pistol grip (many people want to specialize their rifle on the pistol grip as well), then this would be the right lower receiver parts kit for you.

All lower part kits are different. You can get the lower receiver parts kit without the fire control groups or an AR Lower Receiver Part Kit less the trigger and pistol grip. 

Maybe you have a preference for trigger or pistol grip and want to find a kit that does not include the buttons so you won’t have to look for unnecessary parts which were sold for nothing but never would. 

You can always get a kit with a lower receiver kit without a pistol grip or a trigger if this floats your boat but it is certainly for you.

Special Considerations

M4E1 Lower Parts Kit vs AR-15 Lower Parts Kit

Aero Precision manufactures an AR-15 lower receiver and M4E1 lower receiver. These lower receivers differ because the M4E1’s trigger guard is machined into the lower receiver. There’s no need to have a trigger guard in the lower parts kits since it’s not necessary for installation.

Color options

The Aero Precision lower parts kit comes in FDE and black – perfect for matching with your different AR builds.

Like unique colors? Check out the X15 Burnt Bronze Stripped Lower.

Spare Parts

As an Aero Precision dealer, Worth Firearms stocks spare parts and can order them for you as well. As you build, you’ll notice the springs are under a lot of tension when you put them in. I’ve lost many springs and detents while assembling a lower receiver. We can order any spare pieces or parts you need to complete your build.

Stock assembly and parts

No guide to a lower parts kit would be complete without mentioning the other parts to make your lower receiver functional.

Buffer tubes – should you go commercial or milspec? I cannot find a single good reason to go commercial in buffer tube size or stock. The only reason I would buy a commercial buffer tube is if I accidentally bought a commercial sized stock. Aero’s buffer kit includes the castle nut (pick up a castle nut wrench for this – or else you won’t be shooting anytime soon!).

You can purchase the buffer tube separately or with a buffer, and buffer spring. Believe it or not, there are differences in buffers. The rifle buffer will be longer and have a different weight for mitigating recoil properly.

We also really love the Magpul CTR Stock. I mean love it. It’s exactly what a shooter needs on their rifle.


When purchasing lower parts kits or buffer kits, be sure to check out your local gun store and what it has available. 

We offer a low price AR15 builders set in Burnt Bronze and OD Green. You can also buy the AR15 stripped lower, buffer system, and lower parts kit. We also have deals on AR10 sets from Aero Precision.
Aero Precision also offers a great line of bolt carrier groups. We sell these here.

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