Bushmaster AR lower diagram

The Best AR-15 Lower Parts Kits

Michael Crites

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What are the best AR LPKs available?

The Russians have a saying – “a man is not a man until he has broken a horse, fathered a child, and built a house.” We’d add “and built an AR-15” to that list. It’s a bit of a right of passage for every firearm enthusiast — one day you’ll decide it’s time to build an AR.

You’ll spend hours pouring over reviews, diving into the forums and /r/guns, agonized over the nuances of BCM vs LWRC vs Aero, and nail the ideal upper. Be it class 5.56, .300BLK, or something more exotic – then you’ll pair it with the perfect custom, stripped lower. 

Of course, that new Bravo Company lower isn’t much more than an expensive door stop without all the bits that help it come to life.

For new builders, sorting through the various kit options, colors, triggers, & variety of furniture can be daunting. Rest assured – with just a little guidance you’ll be off to the range enjoying your new hand-built AR in no time.

AR Lowers - Group
Lots o' lowers. Without an LPK these are just expensive paper weights.

Comparison of the Best Lower Parts Kits

The Best Lower Parts Kits Reviewed

Best Overall Kit:

This PSA lower parts kit, like most of their PSA-branded products, delivers solid value for money. The PSA MOE EPT Lower Build Kit provides everything you’ll need to complete a stripped lower, which they also sell. 

PSA is a one-stop-shop in any AR build as they have a huge number of options for lower parts kits. We liked this kit due to the price point and that it includes a trigger which is much nicer than mil-spec option.

They take the standard single-stage government-style fire control group, then polish the contact surfaces and coat the hammer and trigger in a nickel finish, reducing friction & drag. The result is a trigger that is smoother than any out-of the-box mil-spec, and makes this LPK a fantastic value.

What We Liked

  • Includes standard combat-style fire control group
  • Upgraded single-stage, target style, trigger  
  • Simple black color-coded scheme
  • Easy to install
  • Quality Magpul components

What We Didn't Like

  • Potential for QC issues
  • Not as tight-fitting as other options

Runner-up:

The CMMG kits are commonly seen in AR builds, and it’s easy to understand why: quality parts in one easy-to-install set. Plus the CMMG kits has nice touches like oversized takedown detents and color-coded bags to help make the build process easier.

What We Liked

  • Made in the USA
  • Takedown pin detents are oversized for easier installation
  • Trigger doesn’t much creep for mil-spec
  •  Color coded bags simplify installation
  • Includes extra springs

What We Didn't Like

  • Some find the grip to be blocky
  • Buttstock not included

Also Great:

Geissele has built their reputation on slick-running ARs, so it makes sense that they’d be in the LPK market as well. The Geissele AR15 Lower Parts Kit is the kit you’ll want if you already have a trigger and pistol grip selected and just need the other components of the fire control group and a trigger guard.

What We Liked

  • Comes with the major AR lower components
  • Crisp, easy-to-use safeties.
  • Fits a wide variety of mil-spec lowers
  • High-quality finish

What We Didn't Like

  • Since they make great triggers, we’d like to see a kit with the fire control group included
  • The magazine release button may need hand fitting

Best Included Trigger:

This kit by PSA has one of the nicest triggers available in any LPK, and we’d recommend it to anyone who’s selective about trigger feel. The ambidextrous safety is a great touch, especially for left-handed shooters.

What We Liked

  • Comes with an excellent single-stage trigger.
  • Has a buffer retainer, which not all kits do.
  • Safety is ambidextrous and has an auto setting.
  • Included a hex key, they know you can’t find yours either.

What We Didn't Like

  • We would have liked to see a grip included.
  • With an auto safety, perhaps a hardened hammer would have been nice.

Best Minimalist Kit:

If you have a stripped lower and need all the bits and pieces to complete a minimalist rifle, this is the way to go. With the PSA MTM Minimalist EPT Lower Build kit, you’ll have built a mil-spec lower with the Mission First Tactical (MFT) minimalist furniture set, which is a go-to setup for many personal ARs. 

If you want a no -frills, minimalist rifle this kit is worth every penny.

What We Liked

  • Comes with a lightweight buttstock
  • V2 style pistol grip 
  • Includes buffer tube
  • Complete kit – nothing additional needed
  • Available in multiple color options

What We Didn't Like

  • Could include a better trigger

What’s a lower parts kit?

 Often the finishing flourish of a build, a lower parts kit contains all the components that you need to complete the lower receiver of your AR-15. Without the kit your gun simply won’t function.

Every AR starts its life as a bare piece of metal (or polymer if that’s your jam), and transforming that piece of metal into a proper rifle or pistol requires a trigger, bolt catch, safety selector, and set of springs. You’ll find at least this much in any lower parts kit. You can also include the lower furniture (grip & buttstock) to round out a complete build kit.

Bushmaster AR lower diagram
This classic Bushmaster lower breakdown gives you a sense of the components involved in both the complete lower and the LPK. While this is a rifle lower, carbine lowers are similar but with shorter buffers, springs, & buffer tubes.

What to Look for in a Quality Lower Parts Kit

AR Lowers - Daniel Defense Lower
This lower uses a mil-spec trigger, but your kit should fulfill the goals of your build.

While it depends totally on you — but in general it’s not a bad idea for a first-time builder to ask for a little help from someone with experience stitching a lower together. 

1. Fit with your build

You’ll need everything your lower doesn’t have. For folks interested in updating or upgrading bits and pieces, you’ll need new springs and a bolt catch – that’s a basic lower parts kit. 

For others who are completing a stripped lower, you’ll need a complete lower parts kit with all of the above plus a trigger, trigger guard, grip, buffer tube assembly & stock.

2. Trigger Assembly

AR Lowers - PSA PCC Lower Alt
This lower's using a single-stage, flat-faced trigger for competition use. Different strokes, as they say.

The lower parts kit influences handling & trigger feel so it pays to choose carefully.

Some kits come with a mil-spec trigger, which works, is relatively inexpensive, and many shooters are comfortable with – but mil-spec may not be your goal. In that case, look for a kit that offers a single-stage trigger for a cleaner break. Some kits will offer various color options on the furniture, so you can impress your shooting buddies with a buttstock that matches your kicks.

You can pick up budget options, but whatever you save in cash will almost certainly be paid out in frustration when you blow a spring or hate the trigger.

3. Completeness

Also, consider what the kit includes. Make sure it includes everything you need to complete your rifle. If you’re missing the fire control group and don’t pick up the right kit, you’ll be right back here looking for parts instead of heading to the range.

In the market for a complete lower? We’ve got a list of some of the best AR-15 lowers available today.

Conclusion

Here, we’ve run down some of the best AR-15 lower parts kits on the market. While they vary in terms of features and completeness there’s almost certainly a kit out there that will have the parts you need. We like the PSA MOE kit, which has the advantage of including all the components you need to fully complete a lower receiver while letting you pick your furniture to finish out your build in the way you want. 

That said, some of the other offerings are compelling for different reasons and may fit your needs better, so we encourage you to check out all your options. Happy hunting!

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