When a shooter is looking to add a sub $500 AR 15 to their collection, there’s little surprise that many gravitate towards the Ruger AR 556. This rifle comes out of the box ready to receive an optic and start shooting 1.5 MOA or better, even with cheap ammunition. As a reliable and affordable rifle, the Ruger AR 556 punches above its weight class in several categories. Though, achieving accuracy from your AR 556 will require you to mount the best scope for Ruger AR 556 for your application.
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What AR 556 Optic Do You Need?
While your AR 556 is a very capable rifle, there are expectations of the 5.56 caliber that need to be understood. This caliber, and the rifle, will be good at engaging targets between zero and 300 yards. While you can hit targets beyond that range, the round becomes less effective and repeatable performance at that range becomes very challenging when you extend beyond 300 yards.
This means that some of your best options for optics will be either red dot sights, holographic sights, or low powered variable optics with some exceptions for higher powered rifle scopes. Your application and preferences will help you to identify which is best for your AR 556.
- Competition shooters – may want to stick with red dot or holographic sights, especially if they compete in the factory division of 3-gun shooting. In this division, no magnified optics are allowed and either of these two optics will help the shooter get on target much faster than iron sights. Other divisions, or other competitions, that allow magnification usually call for a LPVO that is capable of a 1x magnification and up to 8x as a maximum.
- Hunters – will usually want a magnified optic to give them the best chance at hitting the small vital area on their game. When hunting for predators, such as coyotes, you will likely need to have some distance between yourself and your target to have a chance at getting a shot off undetected. LPVOs or moderate hunting scopes will greatly assist the hunter in both acquiring and hitting their targets.
- Home Defenders – are going to be working with close range shots. For this reason, red dots or holographic sights are going to be most beneficial. Prism scopes are also gaining popularity as they give the shooter the long battery life and simple operation of the red dot sight, with the ability to use more complex reticles like you get with the holographic sights. You will need to determine what features are most beneficial for your preferences and budget.
Our Recommendations for Ruger AR 556 Scope
Nikon M Tactical 1-4x
This scope is first on the list because Nikon’s M series is supposed to be some of their more expensive scopes available. While this scope is not the one we’d recommend to take to Fallujah with you, this scope will get you competing on the 3-gun courses.
Nikon is known for having great lens quality with both their coatings and their fine grind, giving you a clear image with plenty of light making it into the scope tube. The scope features a tactical reticle with MOA marks to help with shot corrections at range.
While it might be a tad optimistic to have spring-loaded, zero stop turrets on a 4x scope, it is nice that they took the effort to put high quality components into them. The generous eye relief and the true 1x magnification is what makes scope shine as a competition optic for somebody on a budget. While there are better scopes of this style, keep in mind that you are pairing this to a high-value AR the value of this scope compliments that perfectly.
Primary Arms SLx8
If you are looking for a serious 3-gun scope, the Primary Arms SLx8 is one of the best options available for the AR 556. The price point is on the higher end of what I’d recommend for this rifle, but it’s got all of the features you would want if you plan on taking your AR 556 to competition.
The scope features the ACSS reticle which is widely praised by professionals and enthusiasts for its intuitive methods of assisting the shooter compensate for wind and bullet drop, while also providing tools for range estimation and close quarters engagements. The lenses provide an image that is crisper and clearer than some more expensive brands. With a true 1x magnification and a maximum of 8x, the shooter will be able to quickly transition from near targets all the way out to a couple hundred meters with ease. And of course, the scope is shock proof, waterproof, and can stand up to all of the abuse competitors might put their equipment through.
Vortex Diamondback
If you are planning on taking your AR 556 hunting for deer, coyote, or wild hogs, you are going to want a scope to help you close the distance with your target. This scope does so at an incredible value. The Diamondback can often be found for under $200, and it comes with all of the features you would want in a hunting scope.
The scope is lightweight and has a modest profile, which pair well with the AR 556 as the size of the scope will allow you to mount it relatively low. The lightweight helps to make the rifle easier to manage when trekking through the wilderness. The windage and elevation adjustments are tactile and confidence inspiring, but there are no exposed turrets to complicate a shot during hunting. The reticle has hold over points for wind and bullet drop corrections built in, and the 3-9x is a perfect magnification range for hunting.
Vortex is known for having crystal clear lenses on their scopes, and their coatings will help to prevent fog, glare, and scratches.
Bushnell AR/223
If you want to put your AR 556 to the test and see how far you can reach out and touch some targets, you’re going to need the right equipment to do so. This scope is designed from the ground up to be a precision rifle scope specifically for the AR platform rifle. It is lightweight, has a main tube short enough to fit on an AR receiver without ridiculous mounting hardware, and has a generous eye relief.
The reticle is well thought out with bullet drip compensation up to 500 meters, which is realistic for the .223/5.56 caliber. The reticle is even calibrated for 55-62 grain loads, which are the most common loads used for training.
What this scope has that others don’t are a full set of controls for long range precision shooting. The turrets are prominent and work well, with audible and tactile clicks. The left side of the scope features a parallax control to help mitigate the effects ranges and magnification can have on point of impact. All of that paired with the modest price tag make this the go-to scope when trying to shoot long-range with the AR 556.
Vortex Strikefire II
Built as a budget friendly competitor to the prolific Aimpoint Pro, the Vortex Strikefire II holds its own in the realm of CQB optics. While functionally similar to the more expensive PRO, the Strikefire has some of its own tricks up its sleeve to make it a valid option when looking for a red dot sight.
This red dot sight features the ability to switch between red or green dots, which is something the higher priced competitors often decide to leave out. This is very beneficial to many as some shooters prefer one color over the other, and some believe that different colors perform better in different conditions.
The Strikefire II gets the same coatings on the lenses as many other Vortex products, which means that even though the optic is already well-suited to gathering light it will out-perform competitors with a well-lit tube and resist both fog and glare.
The sight is built on a single piece main tube and comes pre-installed on a cantilever mount that is perfect for mounting on your AR 556.
Holosun 503CU
If you choose to use your AR 556 for home defense, you will need to have an optic that allows you to engage targets in low light conditions. Iron sights are not going to help you in dark rooms when something goes bump in the night. This small, lightweight optic will help you to quickly engage targets at point blank ranges, up to a couple hundred yards away easily.
The optic is often grouped in with red dot sights, but it is actually a prism scope. This means that it can have a more complex reticle than a red dot, but still boast extraordinary battery life. The reticle on this optic is a 65 MOA ring that is great for quickly acquiring near targets, or determining hold-off on further targets, with a precise 2 MOA red dot in the middle. The battery life on this scope is advertised as good for 40,000 hours of continuous use, but it gets even better than that; the optic has a motion sensor that will turn the optic off to save battery after 5 minutes without movement and instantly turn on the moment the rifle is picked up.
The optic also has a solar panel on top which serves two functions. If exposed to sunlight, the optic will run on solar power instead of battery, meaning that technically this optic could continue to work indefinitely without a battery change. It will also help to auto-adjust the brightness of the reticle based on the ambient light; if you ever want to switch to manual mode, one button press exits the auto-brightness setting.
With superb battery life and excellent reticle, this is the most recommended home defense optic for the AR 556.
Bushnell TRS-25
It’s hard to make a list of notable budget optics without including the TRS-25. This is the red dot that gets put on just about every firearm capable of receiving it and getting used and abused beyond what should be expected of a budget red dot.
This is a no-frills optic that just flat out performs. It has a 3 MOA red dot as a reticle, which is more precise than some competitors but not overly exciting. It has adequate battery life. The main tube is nitrogen purged and the lenses are coated to prevent fogging and glare.
If you need an optic to get you on the range, and you’re on a budget, this is the way to go.
ATN X-Sight II
For those who need to be able to find and engage targets at night with their AR 556, this is the way to go. This is one of the most affordable night vision scopes on the market, but it comes with the ATN name and warranty backing it.
The scope features both day and night modes and comes with a lot of the features you will find on more expensive ATN products. An automatic, self-adjusting reticle will take all of the guessing out of compensating for bullet drop at range. The built-in range finder will let you know exactly how far your target is. The on-board recording software will capture every exciting moment you see through the scope when you take that shot.
For budget friendly night vision, this is the scope for the AR 556.
Mounting Your Ruger AR 556 Scope
Mounting red dot and holographic sights are very simple. They often come with a mounting method included or built into the optic, and they will almost always mount directly to the picatinny rail that is built into the top of the receiver on the AR 556. Because these sights have unlimited eye relief, the general rule is to mount them as far forward on the receiver as possible to give the shooter the best field of view and make the reticle small and accurate. If your AR 556 has a handguard with the ability to mount accessories on top, make sure your optic does not touch that rail as misalignment or pressure on the handguard can move your point of aim.
The same rule about keeping your optic mounts on the receiver remains true for magnified optics as well, but there are some other considerations to pay attention to as well. Magnified optics will have a certain amount of eye relief that allows the shooter to have full field of view behind the scope, and that can vary from scope to scope. You will want to place the scope on the receiver where you can comfortably see a full field of view with the scope at maximum magnification. This can often push scope rings beyond the receiver, so you may need to invest in cantilever rings or a cantilever scope mount when putting a scope on your AR 556.
When mounting a scope, most will simply drop a scope into the rings, and tighten them down. To get the best performance possible out of your scope, you should lap your rings to have the most consistently flat and parallel mounting surfaces with the most surface contact with the scope as possible. Lapping your rings is essentially using a very flat rod and a fine sanding compound to remove any rough and uneven spots on the rings that could cause some misalignment of the scope.
Use the great video from the beginning of this section for a full guide on how to lap your rings and install your scope.
Sighting in Your Ruger AR 556 Scope
Regardless of your type of optic, you will need to zero, or sight in, your optic once you have it mounted to your AR 556. One of the ways that you can speed up this process is to use a bore light before you go to the range. A bore light is a laser that shoots out from the barrel of your rifle, and you can adjust your scope to meet that point at home before you ever head to the range. When using a bore light, keep in mind that you are probably aiming at a target less than 15 yards away and your optic is mounted several inches above your bore; measure the distance from the middle of the rifle barrel to the middle of the optic, and make your point of aim the same distance above where the laser hits.
If you don’t have a bore light, try zeroing at 25 yards before you reach out to 100 yards or further. Once again, keep in mind that you will want your point of impact to be lower than your point of aim if you plan on shooting targets beyond that 25-yard mark.
When you are on paper at 25 yards or you have your bore light complete, most shooters will zero their AR 556 at 100 yards. Using three to five shot groups, measure from the middle of that group to the bullseye on the target, and make adjustments until you are cleaning out the red.
Final Thoughts
The Ruger AR 556 is one of the nicer entry level tactical sporting rifles available on the market today. When you have a capable rifle like this, you will want to maximize its potential, and one of the main ways to do that is to make sure you have the right optic for the task at hand.
L.P. Brezny is a highly respected and experienced shotgun expert and author with over 50 years in the industry and testing lab. He has contributed to numerous firearms publications, including Wildfowl, Shotgun Sports, and Varmint Hunters, and is a regular columnist for Gun Digest and AmmoLand News.