Every year we sell thousands of AR 15 lower parts kits. With many of them as part of AR 15 lower build kits. We thought that we should share our bestselling AR 15 lower build kits and explain why they are so popular.
For those who like building every aspect of their AR, the lower build kit is the best way to get all of the necessary parts to complete the stripped lower receiver they purchased from their dealer with an FFL.
What's in a lower build kit?
Everything you need to complete the assembly of a stripped AR 15 lower receiver comes in one package. Known as an AR 15 Lower Build Kit (LBK). An LBK should each contain all of the following:
- Mil Spec Buffer Tube Kit
- Mil Spec Stock Kit or Custom Stock Kit
- Mil Spec AR 15 Lower Parts Kit
When you purchase your LBK from Black Rifle Depot every kit also comes with the BRD Lifetime Warranty to ensure you only have to build your lower once.
How to choose a lower build kit
Just about all lower parts kits are going to come with the same individual parts. The core parts needed for completing the assembly of an AR 15 lower receiver are typically the same. So, you might be thinking it doesn’t matter which kit you purchase then. You would be mistaken however.
Not every lower parts kit is made the same. There are going to be some that are better than others. The last thing that you want is to put together a rifle that is going to have some parts break eventually, this can lead to some major complications within your firearm. It is critical that you buy a lower build kit that manufacturers the parts out of the correct materials, and comes with a lifetime warranty.
Let’s take a look at some of the important considerations when buying a lower parts kit.
Is the kit meant for a new build, or repair/replacement of a damaged part? If you are purchasing the lower parts kit with the intention of repairing your existing AR, then the most important thing is to make sure that the parts are compatible with your current rifle. Due to the many slight differences from each manufacturer, you may want to buy the same one, unless you are replacing a majority of the parts. This will greatly depend on how you customized your rifle is.
If you are like most people, the last thing you want is parts that are prone to breaking. You can often avoid making a bad purchase by simply by reading the reviews on a product. If there are any issues with durability, people who have had trouble will certainly not remain quiet about it.
This may seem like a trivial thing, but parts can come in different colors. If you are building your rifle from scratch or repairing your existing one, you want to make sure that you get the proper color. Mainly because if you buy right, your choice will last you a lifetime.
Our Top Five Best Selling AR 15 Lower Build Kits
1. Mil-Spec AR 15 Lower Build Kit
This Mil Spec AR 15 Lower Build Kit comes with everything you need to complete your AR 15 and variant lower receiver. The AR 15 Lower Build Kit has a 6 position Mil Spec Stock with sling attachment and standard OEM AR 15 Lower Parts kit.
- Complete Mil Spec Buffer Tube Kit w/Stock (American Made)
- Mil Spec Lower Parts Kit (American Made)
- Lifetime Warranty
Pros: This is a great all-around Mil-Spec kit. All parts work together and are covered by a lifetime warranty.
Cons: This is a standard lower build kit, with no frills.
2. SOPMOD AR 15 Lower Build Kit
This SOPMOD AR 15 Lower Build Kit offers a lightweight design with an extended cheek weld for comfort. The snag free shape prevents tangling with the shooters sling and gear. It features an ambidextrous QD Swivel sockets and a removable rubberized butt pad for added shoulder placement. Each SOPMOD AR 15 Stock kit has two water tight compartments for extra gear batteries (or skittles).
- Mil spec SOPMOD Stock Kit (American Made)
- Mil Spec Buffer Tube assembly (American Made)
- AR 15 Lower Parts Kit (American Made)
- Lifetime Warranty
Pros: This is a great upgraded kit. All parts work seamlessly together and are covered by a lifetime warranty.
Cons: This lower build kit only comes in one color option.
3. Magpul MOE® AR 15 Lower Build Kit
The Magpul AR 15 Lower Build Kit from Black Rifle Depot is everything you need to complete your lower build project. The Magpul Lower Build Kit includes a complete mil spec lower parts kit, m4 buffer assembly, Magpul MOE stock, Magpul MOE grip and Magpul MOE polymer trigger guard. The Magpul MOE Lower Build Kit has been tested and throughout the industry and is backed with a lifetime warranty.
- Mil Spec Buffer Tube Kit (American Made)
- MOE Grip (Black)
- MOE Stock (Black)
- MOE Trigger Guard (Black)
- AR 15 Mil Spec Lower Parts Kit (American Made)
Pros: This is a great upgrade kit for anyone who loves Magpul. All parts work seamlessly together and are covered by a lifetime warranty.
Cons: This lower build kit is really only for fans of Magpul products.
4. CQC 4 Position Micro AR 15 Lower Build Kit
This CQC AR 15 Stock Kit has a smaller overall size and eliminating the sling loop allows for more maneuverability in tight quarters. With the AR 15 Stock at an overall weight of 4.9 oz it is almost two ounces lighter over the standard AR 15 Stock kit. This kit includes everything needed to finish your AR 15 and variant lower receiver.
- CQB Mil Spec Micro Stock
- Mil Spec Buffer Tube Assembly
- OEM AR 15 Lower Parts Kit
Pros: This is a great upgrade kit for anyone who wants a small quarters rifle. The smaller size makes it easier to maneuver in tight places. All parts work seamlessly together and are covered by a lifetime warranty.
Cons: This lower build kit includes a smaller stock that only has limited positions.
5. Pistol AR 15 Lower Build Kit
This AR 15 Pistol Lower build kit is for anyone looking to build out their pistol lower receiver. It is not intended to convert a rifle lower into a pistol lower. See your local and national regulation and limitations before purchasing or assembling one.
- Includes Complete Pistol Buffer Kit
- Includes Complete Mil Spec lower Parts Kit (OEM)
- Lifetime Warranty
Pros: This is a great upgrade kit for anyone who wants a pistol. The smaller size makes it easier to maneuver in tight places. All parts work seamlessly together and are covered by a lifetime warranty.
Cons: This lower build kit includes a pistol buffer and is only legal in specific circumstances. It is not a kit that is for everyone.
What if you lose parts?
Having a spring fly across the room when trying to assemble your lower is all part of the fun. It is far less fun however, when you cannot find the wayward part. Do yourself a favor and plan to misplace or lose at least one of the pieces during assembly. With this inevitability in mind, get some spare parts to eliminate the hassle of having to wait for one part to be shipped.
Shop for individual parts
If you are certain that you will only need one single part, you can order it and wait for it to arrive. It is the slow play, but it can save you a few dollars, but probably not much time.
Shop for spare parts kits
Having an oops kit or a spare parts kit can save you not just time, but also headache. Knowing you have a few of each part in the event that it becomes needed helps with relaxed assembly. Not to mention it can make you a life saver if you or a buddy need to replace a small part when out during a day of shooting.
What comes in the AR 15 Lower Parts Kits included in the Lower Build Kits from BRD?
All BRD LPK’s come with:
- Bolt Catch
- Bolt Catch Plunger
- Bolt Catch Roll Pin
- Bolt Catch Spring
- Buffer Retainer
- Buffer Retainer Spring
- Disconnect Spring
- Hammer (Black Oxidize)
- Hammer Pin
- Hammer Spring
- Magazine Catch
- Magazine Catch Button
- Magazine Catch Spring
- A2 Pistol Grip
- Pistol Grip Lock Washer
- Pistol Grip Screw
- Pivot Pin
- Pivot Pin Detent
- Pivot Pin Detent Spring
- Selector Detent
- Selector Detent Spring
- Takedown Pin (Front & Rear)
- Takedown Pin Detent
- Detent Springs (2)
- Trigger (Black Oxide)
- Trigger Guard
- Trigger Guard Roll Pin
- Trigger Pin
- Trigger Spring
- Parts Are in Colored Bags for Easy Assembly
- 100% American Made
What do the Buffer Tube Kits Included in the Lower Build Kits Include?
Each Buffer Tube Kit Includes:
- 6-position Receiver Extension
- Castle Nut
- End Plate