It goes without saying that the AR-15 is, by far, one of the most popular rifle platforms available, owing its status and regard to its adaptability for separate roles. Just about every single component on an AR-15 can be swapped out for another one; not only does this allow you to easily customize your rifle, but it allows you to build one completely to your specifications.
However, without careful planning, you can unintentionally create a rifle that’s heavy and unwieldy. This is why lightweight AR-15 builds have become increasingly popular; they maintain balance and reduce overall weight, making the rifle easier to maneuver and carry for extended periods. Still, there’s a lot to consider before you set out to build an ultralight AR-15.
Considerations for a Lightweight AR Build
What is considered ‘lightweight’?
The definition of ‘lightweight’ is subjective. On average, a stock AR-15, with no accessories, tends to weigh around 6.5 to 7 pounds. Once you’ve added an optic, light, and other accessories, it can increase to 8 or 9 pounds, or more depending on your setup. To some, this is a light build, but depending on your rifle’s purpose, this may be too heavy. For instance, ultralight competitive rifle builds can weigh as little as 5 pounds stock, bringing the total weight to around 6-7 pounds with an optic and accessories.
If you plan to build a lightweight AR-15, there are several factors to consider for maintaining your rifle’s balance between performance and weight savings. While a lighter build can make your rifle easier to maneuver and less fatiguing when carried for a long time, less weight can also lead to a higher amount of felt recoil, making it harder to stay on target. Because of this, you need to be strategic when choosing your rifle’s parts.
Caliber Considerations
Another key consideration is your rifle’s caliber. Most commonly, AR-15s are chambered in 5.56 NATO, which doesn’t produce too much recoil, however, other calibers can differ. Compared to 5.56 NATO, .300 Blackout and 7.62×39 produce considerably more recoil, which is very noticeable in a lightweight build. We recommend sticking with 5.56, but if you intend to use another caliber, outfitting your rifle with a quality muzzle device, such as a muzzle brake, can tame the recoil of your rifle.
The differences in AR-15 calibers can be confusing at the technical level, but our guide, “What Caliber is an AR-15?” breaks down some of the most common ones.
Building a Lightweight AR-15
Part of what makes the AR-15 such a great platform is its ability to be customized for different purposes. With that in mind, you can easily build one out to be as lightweight as possible by choosing the right components.
AR-15 Stock
An AR-15 stock is a crucial part that provides stability and helps you absorb recoil. Most modern AR stocks are fairly lightweight, so their weight generally isn’t much of a concern. Carbine stocks like the Magpul MOE SL, MFT Battlelink Minimalist, and the B5 Systems SOPMOD stock, are some of the best options for lightweight builds, having simplified designs and minimal weight. If you’re wanting to shave off even more weight, options like the Lancer Carbon Fixed Stock weigh less than 9.5 ounces and still boast incredible structural integrity.
AR-15 Handguards
AR-15 handguards not only protect your hands from the heat of the barrel, but they also serve as the mounting hub for most, if not all, of your rifle’s accessories. Lightweight handguards are available in multiple materials, such as aluminum and carbon fiber. Aluminum handguards, like those from BCM and Geissele, feature more streamlined designs with M-LOK support. Their weight can vary but depending on the configuration you choose they can weigh around 10 ounces, making them much lighter than something like thicker quad rail option.
Carbon fiber handguards are remarkably light, sometimes weighing as little as roughly 7 ounces. These handguards still have mounting capabilities like M-LOK support and they’re rigid enough to retain zero, allowing you to easily mount laser units. However, they aren’t as resistant to shock and impact as aluminum ones. It’s unlikely, but they can crack or break if dropped. This isn’t to say that they’re a bad option though as both Faxon Firearms and Lancer Systems offer high-quality carbon fiber handguards.
AR-15 Barrels
An AR-15 barrel is, inherently, one of the heaviest components present in any build. Their weight can be significantly reduced by opting for different barrel profiles, fluting, or varied materials entirely.
Pencil profile barrels are a great option for lightweight builds. They’re much thinner and lighter than other AR-15 barrel profiles. Still, their thin shape makes them prone to overheating, especially when firing rapidly. You could also go with a fluted barrel. Simply put, flutes are a series of grooves that are cut into a barrel to reduce their weight. These grooves increase the surface area of the barrel, making it cool down faster, but it also allows you to use thicker profile barrels with the added benefit of weight reduction.
Carbon fiber barrels are some of, if not, the lightest AR-15 barrels available. Essentially, they’re a much thinner steel barrel that’s reinforced with carbon fiber, making them incredibly light and strong while also offering solid heat dissipation and rigidity. CF barrels require expensive materials to produce them, so they can cost upwards of $750+ depending on which model you look at.
To get an idea of how different barrels stack up against each other, our guide on the best AR-15 barrels goes more in-depth on each.
Lower Receivers
AR-15 lowers receivers are typically made of 7075-T6 aluminum, which is known for its high strength and durability. As for lightweight options, it’s hard to beat the standard mil-spec lower. Made of forged aluminum, they weigh around 8.5 ounces. In addition to mil-spec lowers are billet lowers, which are milled instead of forged into shape. Manufacturers often add unique features in these lowers, like ambidextrous mag releases and bolt catches, but they tend to run heavier than mil-spec options.
However, you can reduce the weight by opting for a skeletonized lower, which are functionally the same, but most of the excess material is removed to reduce weight. Different brands use different lightning cut patterns, but they all achieve the same goal. Although skeletonizing is more common on billet lowers, there are select forged lower options that come configured this way as well.
Upper Receivers
Much like with lower receivers, upper receivers on their own aren’t all that heavy to begin with. They’re often made from the same 7075-T6 aluminum that lowers are made from, and there isn’t much weight to reduce when looking at them. If you’re really trying to save weight, you can opt for an upper that doesn’t have a forward assist since it will have less material overall. Just bear in mind that these weight savings are negligible at best, and you likely won’t notice too much of a difference when your build is complete.
Optics
Should You Put a Red Dot or a Scope on Your Rifle?
Which optic to use depends entirely on the application you’ve built the rifle for. If you’ve built an AR in an SPR or other long-range styling, it’d be more beneficial to run a variable power riflescope that’s better equipped for shooting at long-distance. Likewise, if you’re building a home defense rifle, or something for competitions where speed and agility are a priority, a red dot sight is a much better option. If you’re working with a general-purpose rifle and want to blend both styles of shooting, a red dot and magnifier combo, or an LPVO would work great too.
Magnifiers are an added optic that mounts behind your reflex sight, and when in use, magnify the sight picture and reticle to make it easier to accurately use your red dot at distance. An LPVO, meaning Low Power Variable Optic, is more akin to traditional rifle scopes, but instead of having large magnification ranges, they’re offered in smaller ones, with them usually being found in a 1-6x, 1-8x, or 1-10x configuration. Both are an excellent choice, but they each come with their pros and cons.
Holographic Sights
Holographic sights are another type of reflex sight, but they have some distinct differences and advantages. Instead of reflecting light back from one surface, it’s bounced off many to create a holographic reticle that floats in between the lenses of the optic. Thanks to this design, they’re essentially parallax free so long as you’re using them in their usable range, and they pair excellently with magnifiers.
However, they come with their disadvantages. Holographic sights have much shorter battery lives than red dot and open emitter reflex sights, and because of their design, they’re much heavier than them as well. While a holographic sight can be an exceptional addition to your rifle, if you’re trying to save on weight, it may be better to opt for a standard red dot or reflex sight choice.
Prism Scopes
Prism scopes are another solid optic choice for lightweight AR builds. Essentially, they’re a blend of both variable power optics and red dot sights. Instead of using an emitter to project a reticle onto the objective lens of your optic, prism scopes have etched reticles, like rifle scopes. Because of this, the reticle can be seen without illumination, and they’re much easier to use if you have astigmatism.
With a few very irregular exceptions, prism scopes have fixed magnification. Modern 1x prism scopes are just as quick as red dot sights and select models like our SLx® 1x MicroPrism™ Scopes are compatible with magnifiers as well. If you need to reach further, MicroPrisms are also available in either a 3x or 5x magnification level. When you’re using a magnified prism scope, you can run an offset red dot sight if you want to quickly switch between magnified and unmagnified use.
There are often debates amongst enthusiasts over prism vs. red dot sights. If you’re on the fence about which to use, our guide highlights their advantages.
Accessories
With your rifle build and optic selected, your build is functionally complete. That said, there are still some ways to enhance the adaptability and overall utility of your rifle.
Slings
Slings are more than just an aid for carrying your rifles when on the move. When mounted properly, they greatly disperse the weight of your rifle, making it easy to carry and stow without causing as much fatigue. This may seem unnecessary since almost every point thus far has been about making your rifle as light as possible, but carrying a light rifle can be tiring when doing so for extended periods of time. Also, in dynamic shooting scenarios, like competitions, getting a two-point sling for your AR-15 ensures that the rifle stays secured to your body, allowing you to easily transition to a handgun.
Weapon Lights
Weapon lights are a staple on any rifle. As their name suggests, they’re great for illuminating and identifying targets in low light environments, making them an excellent choice for home defense rifles. Although AR-15 lights don’t usually weigh that much, every ounce matters on a lightweight rifle. Models like the Surefire Scout are among the most well-known weapon light models, but their Mini Scout Light Pro is smaller and weighs less, albeit at the cost of having less power.
Conclusion
Building a lightweight AR-15 take a lot of consideration, and while it can pose a challenge to new enthusiasts, it isn’t an impossible task. Each part, from the barrel to the stock, plays a crucial role in keeping the utility of your rifle, so while it may be tempting to go for the lightest components possible, remember that at the end of the day, it’s all about finding the right balance.
Whether you’re building your rifle for home defense, competitions, or long-range shooting, choosing the right components for your build is crucial, as each one plays a significant role in the final product of your build. While you’re piecing together your rifle, continue taking time to research the options available to you. If they meet your needs and preferences, you’ll be good to go.
If you’re thinking that an ultralight AR-15 isn’t the move right now, you might benefit more from a different style build. Check out our guide on the best AR-15 setups. It highlights different build types and what to consider when building your next rifle.
