The AR-15 platform is popular among gun owners for a number of reasons. One of these is the unlimited customizability that the design offers. But what upgrades do you really need?

Gun owners prize the AR-15 for its customizability, and the market for accessories and upgrades is considerable. The purpose of an upgrade is to enhance the function of your rifle in some way. Many upgrades and accessories are necessary or desirable because they solve a problem.
AR-15 Upgrades
Whether you’re building or modifying a rifle, some AR-15 upgrades are highly recommended and considered mandatory to improve the function of your rifle or your ability to shoot it.

Sights
Standard iron sights, consisting of a front post and a rear aperture, are reliable and straightforward. If your rifle doesn’t have at least these, you should buy a set, preferably metallic. However, if your rifle already has a set of iron sights, you should consider upgrading to a reflector, holographic, or prismatic sight if your budget allows for it. Alternatively, depending on the ranges you expect to fire your rifle, you may decide to buy a low-power variable optic (LPVO).
Magazines
Reliable, durable magazines are essential for the operation of your semi-automatic rifle. G.I. magazines aren’t always of satisfactory build quality. Faulty magazines are also one of the most common causes of failures to feed. Some of the features you should aim for in replacement magazines are a corrosion-resistant stainless-steel feeding spring, an anti-tilt follower, and a textured body that increases grip for removal.
Optional
Most upgrades for the AR-15 rifle are specific to the user or application and can be considered optional.
Charging handle upgrades
The standard charging handle is sufficient for most purposes; however, if you’re a competition shooter, you may want to increase its ambidextrous functionality so that you can charge the weapon with either your right or left hand. Some shooters may prefer to substitute a side-charging handle, thereby eliminating the T-shaped design entirely. One of the primary advantages of the side-charging design is that you can charge the weapon against a door frame, belt, or other surfaces in an emergency.
Trigger upgrades
A good trigger can be beneficial to accurate shooting. If you shoot competitively, competition triggers that allow you to adjust the weight, overtravel, and reset can significantly improve your performance when seconds count. For benchrest or precision shooting, a light, crisp trigger will surpass the stock mil-spec.
M-LOK, KeyMod, or quad-rail handguards
If you want to attach accessories, such as a weapon light, bipod, vertical or horizontal foregrip, you’ll need a way of doing that. Handguards that provide rails or locking slots can be vital for this purpose.
It’s also worth noting that free-floating handguards, which do not contact the barrel, will interfere less with the barrel’s harmonics during firing.
Lights
If you keep a rifle for home defense, one of the most useful AR-15 upgrades or accessories that you can buy is a dedicated weapon light with a push button or tape switch.
In fact, for a home-defense rifle, this is required. The reason it’s listed as an optional upgrade is that many AR-15 owners keep the rifle for recreational and competitive target shooting.
This allows you to illuminate your environment and target in an instant, providing positive identification of the threat under low-light conditions. You can’t shoot what you can’t see. So this is one of the most important upgrades for a defensive rifle.
Sound suppressors
This is in the optional category because of its varying legal status. An upgrade or accessory shouldn’t be mandatory if it’s not generally available. The primary purpose of a sound suppressor in a civilian context is safety — it reduces the risk of permanent hearing loss. It also decreases noise pollution, which is becoming increasingly important for those who manage outdoor firing ranges.
Muzzle brakes/compensators
A compensator can stabilize the rifle for those who shoot competitively, allowing you to shoot more rapidly without compromising accuracy. However, if you only shoot recreationally or engage in slow fire on the range, a compensator is not critical. The inclusion of a muzzle brake can be useful for minimizing the felt recoil of heavy calibers, such as .50 Beowulf. These types of devices are optional according to the caliber and application.
Trigger guard
If you fire your rifle in colder climates, which require the use of heavy gloves, you may want to install an oversized trigger guard.
Stocks
The standard collapsible butt stock is probably sufficient for most purposes. However, if you want to upgrade the stock, you can choose one with an adjustable cheek piece, allowing you to raise the comb. If you fire heavier calibers, you may also want to look into rubber recoil pads.
Slings
A sling isn’t simply for carrying your rifle — it also lets you stabilize the weapon for accurate shooting. There are several types of slings to choose from, ranging from single- and two-point slings to Ching slings and other devices.
Bipod
A bipod consists of two legs that support the front of the rifle on the ground or another horizontal surface, providing a rest for stable prone and benchrest shooting. If you want to test the inherent accuracy of your rifle, a bipod can help.
Bipods can provide you a better precision on every terrain you are on which makes your every shot counts.
Ambidextrous controls
These AR-15 upgrades are optional unless you’re left-handed. If you’re a southpaw, you may consider these enhancements mandatory for improving ergonomics. These include bolt catches, magazine catches, and safety selectors.
Loophole upgrades
This is the simplest way of describing it. A loophole upgrade alters the function of your rifle in some way to legally circumvent restrictive gun-control legislation, which you would encounter in states like California.
An example would be kits that allow you to remove the empty magazine by separating the upper receiver from the lower. This type of upgrade is optional because it’s not necessary in less-restrictive states. It’s tailor-made for a handful of states, bypassing the need for a so-called bullet button or field stripping.
Needless
The AR-15’s modularity and popularity have increased the demand for upgrades that don’t provide a meaningful enhancement to what is essentially a tool. There’s also the problem of gun owners saddling their rifles with gear that they have no use for, increasing the weight and bulk of what would otherwise be a light carbine.
For example, a set of offset or angled sights, allowing you to transition between close- and medium- or long-range targets, can be useful for tactical training or competitive target shooting.
However, if you bought a set of backup sights for a safe queen, a gun that is never used or part of a collection, you’re not getting the most use out of this equipment. Instead, try to figure out exactly what benefits you on a rifle and what doesn’t.
In Conclusion
What ultimately determines whether an upgrade is mandatory, optional, or needless is whether it’s useful to you. You should strive for performance, not gadgetry. This means training and practice.
Choose the upgrades that do what you need. Don’t be swayed by unnecessary marketing buzz.