AR-15s are among the most versatile firearms in existence. They are available in dozens of calibers ranging from rimfire and pistol cartridges all the way to shotgun shells. They can be built to nearly any barrel length, accept just about any class of accessory, and offer an unprecedented diversity in make, model, and materials.
No matter what the application for your next rifle, an AR-15 can handle it. But, it needs to be properly built for the task. For many purposes, a mil-spec rifle fresh off the rack from your local gun store simply won’t do.
The incredible customizability of the AR-15 platform is one of its greatest strengths, but with so many options, it can be a bit overwhelming trying to figure out where to start.
Below, we’ll take a look at some of the best AR-15 builds for three of the most common applications for these rifles: home defense, long-range precision, and general, all-purpose rifles.
Home Defense
One of the most common purposes for modern firearms is the defense of self and home. While handguns remain the most popular option for concealed carry and general self-defense, AR-15s are rapidly becoming one of the more popular options for the protection of one’s home.
Defining the Use Case
Home defense is the most specialized use case on our list. It entails a very narrow set of circumstances, many of which are defined in advance, making it easy to tailor a firearm to the application precisely.
For instance, because the firearm is intended to be used exclusively within the home, we can specify the maximum required effective range quite precisely by simply measuring the longest line of sight within the home. As such, the average home defense firearm does not need to concern itself much with range, since few homes will have a single line of sight exceeding even 25 yards, and nearly any rifle round out of a reasonable barrel length will be effective at those distances.
Because this is a defensive firearm, reliability is a high priority, as is speed and ease of use. It needs to be capable of fast, accurate shots at short distances and should be capable of being deployed effectively in the broadest range of circumstances possible. Higher capacity is generally preferred, but given that the average number of shots fired in a defensive use is quite low, it is not a high priority.
Since it will be used indoors, possibly within tight confines if the home is older or features narrow hallways, the firearm should be as short and maneuverable as possible.
Caliber
For our home defense build, the best calibers boil down to 5.56x45mm NATO or .300 Blackout.
5.56 NATO benefits from commonality, meaning that there is a wealth of high-quality ammunition options available, as well as high-quality barrels. It’s also the most common caliber for AR-15s, so if you plan on buying a complete rifle rather than building, you’ll have many more options in 5.56.
.300 Blackout, on the other hand, offers the potential for a shorter barrel while maintaining efficacy, and in some cases improved terminal ballistics. While 5.56 AR-15s rarely feature barrels shorter than 10.3″, .300 Blackout rifles frequently utilize 8-9″ barrels, or occasionally even shorter.
Either caliber will make a fine option for a home defense AR-15.
Barrel Length
We want this rifle to be as compact as possible and the easiest way to accomplish that is to utilize the shortest barrel practical. However, since barrel length is regulated in the U.S., the decision is not as simple as just picking the shortest barrel you can find.
To keep your rifle out of NFA territory, you’ll need to maintain a barrel length of at least 16 inches. However, you can still shave a few inches off by combining your barrel and muzzle device of choice through pinning and welding, so long as the result exceeds 16 inches in length. A 13.7″ barrel can be combined with one of several suppressor-ready muzzle devices and pinned and welded to meet this requirement.
If, on the other hand, you don’t mind a bit of extra paperwork, you can file the proper forms with the ATF to make or buy a short-barreled rifle. With an approved stamp, you can legally utilize any barrel length. In this case, you should select the shortest barrel that will maintain ballistics effectiveness and reliability for your selected caliber.
Rifle Specifications
The remainder of the rifle can largely be built out to personal preference, but many users will find features such as ambidextrous controls to be useful. For additional maneuverability, users can select a compact stock such as LMT’s PDW buttstock.
A high-quality trigger is a boon to nearly any rifle build, but particularly so in this case. A defensive rifle needs to be capable of firing quickly and precisely—both goals which are aided by a shorter, lighter, or smoother trigger pull. Options from Geissele and Hiperfire are popular for this type of use.
Beyond these essential parts, benefits become marginal, but a short-throw safety can be easier and faster to actuate than a traditional safety for many users, shaving a fraction of a second off of the time it takes to engage a threat.
Muzzle devices can largely be chosen according to preference, but we recommend avoiding aggressive brakes or compensators. The use of these devices indoors will compound the amount of noise and blast experienced by the user, and the recoil-reducing benefits are often negligible with 5.56 or .300 Blackout.
The ideal muzzle device for this setup is, of course, a suppressor, but like short-barreled rifles, these devices are subject to NFA restrictions. Still, no other muzzle device to match the noise and blast-reducing capabilities of a suppressor.
Optics
Since a home defense rifle is intended to be used at short range and in extremely high-stress situations, a red dot or similar optic is ideal. This allows the user to maintain focus on the target while acquiring a sight picture, rather than shifting their focus to the front sight post, as is generally required by iron sights.
Additionally, red dots are particularly well-suited to low-light scenarios, since they are internally illuminated and visible in both absolute darkness and the harsh shine of a weaponlight.
Ideally, a red dot that can be left on continuously for an extended period of time or that is equipped with motion-sensing technology should be selected. Either option will allow the firearm to be stored ready for use at a moment’s notice, requiring no buttons or dials to be actuated to make the firearm operational.
For users with astigmatism or those who prefer an etched reticle, a prism with little or no magnification, such as the Primary Arms SLx 1x MicroPrism, is also a perfectly suitable choice.
Accessories
There are only a few must-have accessories for this build. First and foremost is a weaponlight. Defensive firearms should always be equipped with a light, as they might be needed at any time of day. Most users would be best served by a light that prioritizes flood over throw, although there are techniques that allow highly focused weaponlights to be used indoors with great efficacy, so this is partially a matter of training.
A sling is similarly highly recommended. Having your firearm slung makes it more difficult for it to be removed from your body during an altercation and also allows you to free your hands to flip light switches or turn door handles more easily.
Other accessories, such as grips, hand stops, and so on, are largely up to the discretion of the user, but we would generally recommend keeping any additional accessories to a minimum. The more odds and ends you bolt to your rifle, the more complex you make its operation, and complexity is the exact opposite of what you want in a high-stress situation.
Summary
For a home defense rifle, you want something short, handy, and simple. A red dot, light, and sling are all good additions, but other accessories should be avoided, except for perhaps a foregrip or handstop if preferred.
For a factory-built rifle, the Sons of Liberty Gun Works M4-EXO3 is an excellent option. It’s available with a 13.7″ with a pinned and welded muzzle device, bringing the length over 16″, making it available without any NFA forms needed. SOLGW has an exceptional reputation for building reliable and high-quality rifles, so you can trust that it will function when you need it.
Long-Range Precision
At first glance, an AR-15 may seem an odd choice for a long-range rifle. In a field dominated by AR-10s and bolt-action belted magnums, the small-framed AR-15 seems underpowered.
In the past, this was true; however, innovations in modern ballistic technology have led to new cartridges that both fit in an AR-15 platform and are fully capable of hits at 1200 yards or more.
While the AR-15 may not be able to match higher-caliber competitors at extremely long ranges, 1200 yards is certainly far enough to be considered long-range, and often, this capability significantly outdistances the ranges the average user has access to.
Defining the Use Case
The use case for this type of rifle is exceptionally simple: we want it to be capable of hitting the smallest possible targets at the longest possible distances. This means prioritizing accuracy and velocity above nearly all else. Where possible, recoil should be minimized as well.
Since these types of rifles are fired almost exclusively from a stable, supported position, weight and length can be ignored almost entirely; in fact, a heavier overall weight can help tame recoil. While reliability is valuable in any firearm, these types of rifles are often precisely tuned to operate with minimal recoil, which can cause some cycling malfunctions with lower-recoil rounds. This is generally considered acceptable for target rifles, although competitors may not be well-served by such a trade-off.
Caliber
Standard 5.56 ammo is sufficient for many long-range applications, particularly for users who lack access to ranges in excess of 800 yards. Choosing a common ammunition type makes it easier to locate match-grade ammo, and allows for inexpensive ammo to be used for practice at shorter ranges.
However, for those with the facilities available to engage targets at farther distances, more capable rounds such as 6mm ARC, .224 Valkyrie, or 6.5 Grendel should be used, as they offer superior drop profiles and the ability to resist wind drift, which translates to easier shots at intermediate ranges and the ability to engage targets that would be impossible or highly difficult with 5.56×45.
Magazine capacity is also typically not a priority, although it may be a factor for certain types of competitions. For benchrest use, though, smaller magazines with lower capacities will often allow users to achieve a lower, more stable position on the bench.
Barrel Length
Velocity is essential to minimizing drop and reaching targets at extended ranges, so longer is generally better when it comes to barrel length for precision rifles. However, extremely long barrels can exhibit less rigidity, which can in some cases translate into slightly less precise groups to do the increased movement or “whip” of the barrel during firing, unless the profile is heavy enough to maintain rigidity over the barrel’s length, as is the case with bull barrels.
Additionally, while weight is a non-issue for benchrest or target rifles, those intending to compete or practice long-range marksmanship from unsupported positions will need to consider the overall weight of their rifle. A heavier rifle will be more fatiguing to stabilize from a barricade or unsupported position.
For 5.56 rifles, a 20″ barrel is often a good middle ground, delivering excellent velocity without becoming excessively cumbersome. A 24″ or 26″ barrel will offer more velocity, though, for those intending to use their rifle solely from a bench.
Rifle Specifications
Repeatability is an essential part of accurate marksmanship. You want your head position, trigger press, etc. to be as consistent as possible, shot after shot. Your rifle should be built to support this goal.
First and foremost, this means a top-quality match-grade trigger. The make and model are not particularly important—everyone has their preference, and for nearly every brand out there, there is a user printing excellent groups with it. Choose any trigger you like, so long as it has an appropriate weight and a smooth, clean, consistent break.
You’ll also want to consider your rifle’s ergonomics. A rigid or fixed stock that can be finely adjusted for length of pull and cheek position will help you maintain a consistent head position.
Many users also prefer grips with a very high angle to create a more comfortable hand position when fired prone or from a bench, although you may prefer a more traditional grip if you intend to fire offhand or from improvised positions. In any case, a comfortable grip will be a boon to your practical accuracy.
A free-floating handguard is highly recommended. Both firing from a position in which the weight of the rifle is resting on the handguard or from a loaded bipod can alter your point of impact if using a traditional handguard, but a quality free-floating handguard will prevent this effect.
Ambidexterity is not typically a priority with precision rifles, so upgraded safeties, mag releases, and charging handles can be ignored.
Optics
Obviously, this type of rifle is best served by a scope. Hitting targets at truly long ranges is impossible without magnification, even for the most accomplished marksmen.
For a target rifle, more magnification is generally better. The more powerful your optic, the more precisely you’ll be able to situate your crosshairs, and as the saying goes, aim small, miss small. However, optics with a relatively high minimum magnification, such as 6-30x, can make locating targets at intermediate distances or tracking moving targets difficult.
Both tasks are occasionally involved in certain types of competitions, so if you plan on using your rifle in that way, you’ll want to stick to a more moderate power range. 3-15x, 4-16x, or 3-18x scopes all offer plenty of magnification to take a 5.56 gun to the limit of its range, but if you opt for a cartridge with longer reach, such as 6mm ARC, you may prefer a more powerful scope, such as a 4.5-27x.
Regardless of power range, you’ll want a scope with manual parallax adjustment and the best glass you can afford. Parallax adjustment is essential for precise shot placement at longer distances, and image clarity, quality, and fidelity all become increasingly important the farther out you try to shoot.
While illuminated reticles can be helpful for low-light target engagement, they are typically not required for target rifles, which tend to get used during the brighter hours of the day.
Accessories
If you plan to do any of your target practice prone or from a bench, a bipod is an essential accessory for a precision rifle. A bipod allows you to stabilize the rifle to a much greater degree than would be possible freehand or resting on a barricade.
Of course, a sandbag is another viable option, but we’re partial to having our stabilizing device attached to the rifle, rather than having to carry it around separately.
Some flavor of anti-cant device is also advisable, whether standalone or built into your scope mount. These simple devices are essentially just a specialized bubble level, but they are exceptionally helpful in ensuring that your rifle is perfectly vertical. Any amount of cant can influence the drop profile of your round relative to your point of aim and cause a miss at truly long distances.
If you’ve got money to burn, you can also consider weapon-mounted rangefinders and ballistic calculators, but it’s generally much more cost-effective to use handheld versions of these devices.
Accessories such as weaponlights and IR units are typically unnecessary on these rifles since they are not intended for use at night and are not usually practical with night vision.
Summary
Long-range precision rifles are all about velocity and accuracy. To that end, you want a long, rigid barrel that maximizes velocity and minimizes whip, and accessories that contribute to a clean trigger press and stable, repeatable position.
For a factory option, consider the Daniel Defense MK12. Inspired by the military rifle of the same name, the DD MK12 features an 18″ cold-hammer-forged barrel with a remarkable reputation for accuracy and a Geissele SSA-E trigger.
All-Purpose
The idea of a do-all rifle is attractive for obvious reasons, chief among them that it eliminates the cost involved with setting up multiple specialized rifles and instead allows you to invest in a single, high-quality setup. Of course, no one firearm is going to meet every need—there’s simply no way you’re ever going to be able to shoot skeet with the same rifle you use for long-range precision—but with an AR-15, you can cover a startlingly broad range of uses with just one gun.
Defining the Use Case
The use case for this build is somewhat nebulous; the idea is to be able to cover the widest range of use cases possible. We want a rifle that is as capable at 5 yards as it is at 500, that is short and handy enough to be used in confined spaces but still has enough velocity to reach out to intermediate ranges, and that sports a diverse enough range of features and accessories to be prepared for as many scenarios as possible, both expected and unexpected.
Caliber
5.56 is the undisputed king for this application. The ubiquity of the round means that you can find anything from heavy-for-caliber precision match rounds, to short-range defensive cartridges, to specialized tracers or frangible training ammo with relative ease.
The 5.56x45mm cartridge is also cheap enough that training won’t break the bank—an essential consideration for an all-purpose build. While your rifle will certainly be capable of making hits at 500 yards, it will be considerably more difficult to do so with a general-purpose rifle than it will be with a more specialized build, so proper and thorough training is a must.
Lastly, 5.56×45 is among the most versatile cartridges available when it comes to range. Its reach is greater than that of .300 Blackout or .350 Legend, but it offers considerably less recoil than 6.5 Grendel or 6mm ARC. This makes it perfect for an all-purpose build.
Barrel Length
We want enough velocity to take full advantage of the 5.56’s ballistic potential, so you can typically rule out the shortest barrel options. But, you also want the rifle to be compact and handy enough not to be cumbersome at close range, so you can also eschew longer, precision-oriented barrels. This leaves us with the middle range.
A 16″ barrel is the simplest solution, but a 14.5″ barrel with a pinned and welded muzzle device would serve equally well. We would avoid going shorter than 13.7″ for this type of build; any shorter, and you start to give up enough velocity that making hits at 500-600 yards will become troublesome for the average marksman.
Rifle Specifications
Since we want this rifle to be able to be used for fairly precise shots out to at least moderate distances, a free-floating handguard and match-grade trigger are important components, for the same reasons as in our long-range precision build.
However, for this build, we’d avoid fixed stocks or high-angle grips, as they limit the rifle’s usability in other applications. Instead, a quality adjustable stock and the grip of your preference would be appropriate.
Ambidextrous controls, short throw safeties, and upgraded charging handles are all nice to have, but probably not essential. Few applications truly require these upgrades, even if they are convenient for many.
A flared magwell would be a worthwhile inclusion, particularly if you ever intend to compete with your rifle or use it with night vision, as it can make the reloading process faster and easier to do without having to look down at your rifle.
The muzzle device is primarily a matter of personal preference, although we would be hard-pressed to argue against a quick-disconnect suppressor for a general-purpose rifle. The reduced noise and concussion of a suppressor are convenient for nearly any application, and the ability to quickly remove it significantly ameliorates the drawbacks of the added weight and bulk.
Optics
When it comes to optics, you have a wide range of options. You’ll want to avoid high-powered scopes, which will be all but unusable for fast, short-range work, as well as standalone unmagnified optics such as red dots, which will limit your ability to engage targets at range. Beyond that, though, the sky is the limit.
Low-power variable optics are one of the most popular choices, owing to their versatility. While they are not as fast or intuitive to use as a red dot, an LPVO with a true 1x minimum power is still very capable at close range. An offset or piggyback red dot can also be added for short-range target engagement.
A red dot and magnifier combo would be another suitable option. Similar to an LPVO, a red dot and magnifier combo offers capability at both short and intermediate ranges, although it is biased a bit more towards short-range use. A prism and magnifier or prism and offset red dot would provide a great deal of versatility as well, so this category can largely be determined by personal preference.
Accessories
We want to be prepared for as much as possible this rifle, and that means equipping it with a broad range of tools. A sling and weaponlight are essential, for the same reasons that they are included in our home defense build.
Heavier accessories like bipods should typically be avoided, though, as the increased weight and bulk are detrimental to the bulk of this rifle’s uses, even if they are valuable for long-range use.
If you own a head-mounted night vision device, then an IR unit of some variety should probably have a place on your all-purpose rifle. A unit with both an IR aiming laser and an illuminator would offer the most versatility.
Summary
An all-purpose rifle is a hard thing to define. It tries to thread the needle between long-range efficacy and short-range performance, being handy but not underpowered, accurate but not cumbersome. As such, it inevitably ends up being a jack of all trades, but a master of none, with a common cartridge, intermediate barrel length, and broad smattering of features and accessories.
Because everyone’s idea of an all-purpose rifle is going to be a little different—some might have a home defense or long-range gun already, and so exclude that use case from their “all-purpose” build and focus instead on greater performance in another category—it’s impossible to select any one factory built rifle as the best.
A standard, high-quality AR-15 like the Colt Enhanced Patrol rifle would be a suitable starting point for an all-purpose build, though. It features most of the main attributes we’re looking for, such as a free-floating handguard and 16″ barrel. It even comes with ambidextrous safety levers straight from the factory.
Alternatively, another good option would be to start with a basic but reliable rifle like the much-loved Smith & Wesson M&P Sport 2 and slowly build out your perfect all-purpose build from there.
Conclusion
AR-15s are capable of fulfilling nearly any role required, so long as they are built properly. By choosing the right accessories, components, and cartridge, you can customize your build to tackle the task at hand without issue.
