The best scope for M4 can help improve your M4’s sight, which is the key in yielding the highest level of accuracy in terms of tactical shooting and hunting. You need the best M4 optics and scope in maximizing the overall performance of your rifle because you will be receiving crisp and clear images all the time.
The M4 carbine is actually the evolved version of the M16 rifle. It often features a 14.5-inch barrel, which is not actually legal to own and carry. However, because of the huge increase in the number of M4 enthusiasts, most of them thought of a way to legalize their ownership of the rifle. They do so by creating an M4 that has an additional 1.5-inch barrel.
Still, the authentic M4 carbine is still an effective sporting and tactical rifle that is well-loved by many. Due to its popularity, it is no longer surprising to find people who wish to improve its performance. Fortunately, highly reliable scopes and optics for the M4 are now available, such as the ones reviewed in this article.
Quick Answer: The 13 Best M4 Scopes & Optics for 2020
- Vortex Optics Spitfire 3X Prism Scope
- Primary Arms 2.5x Compact Prism Scope
- Vortex Optics Strike Eagle 1-6×24 – BDC (MOA) Riflescope
- Bushnell AR Optics Drop Zone-223 BDC Reticle Riflescope
- Trijicon ACOG 4×32 Scope Dual Illuminated Chevron .223 Ballistic Reticle
- Nikon P-tactical .223 3×32 Matte BDC Carbine
- Aimpoint PRO Patrol Rifle Optic
- Bushnell TRS-25 Red Dot Sight
- CVLIFE 1x22x33 Red Green Dot Reflex Sight
- Sig Sauer ROMEO 5 Red Dot Sight
- EOTECH 512 Holographic Weapon Sight
- Vortex Optics Razor AMG UH-1 Holographic Sight
- EOTECH EXPS3 Holographic Weapon Sight
First, let’s take a look at the top-rated M4 scopes & optics, then we’ll talk about how to choose the right one for you in our buying guide below.
Best Scopes for M4 Carbine Reviews of 2020
#1 Vortex Optics Spitfire 3X Prism Scope
The first out of the many high-quality scopes for the money that I intend to highlight is the Vortex Optics Spitfire Prism Scope. This is a top pick in many legitimate reviews and buying guide articles as it contains several useful features being incorporated in a compact but rugged and sturdy construction.
I noticed that it suits shooting at a close range and at a medium range distance the most. It also delivers an incredible performance when planning to enjoy quick target acquisition and in many other instances when speed and accuracy matter. It possesses a fully multi-coated lens, which also features an anti-reflective coating.
This lens performs well when it comes to delivering bright and clear views even when you are using it in an environment with low light. I like the 5 brightness levels incorporated into its illuminated red or green EBR-556B reticle.
It is because the presence of these variable settings make it possible to match them in various lighting conditions in the specific environment where you are shooting. I also love this scope because the reticle is directly attached to the prism, giving you an efficient point of aim all the time.
This is possible whether you use the illumination feature or not. I like the special O-ring added into this scope because it works in locking out extra debris and moisture. I am also happy with the prism-based style used in this M4 scope because it promotes sharp and clear optics.
The fixed 3x magnifier is also more than enough for the benefit of most users.
#2 Primary Arms 2.5x Compact Prism Scope
I am also delighted that I came across Primary Arms Compact Prism Scope as I was able to learn how compatible it is with the M4 carbine rifle. It is also a popular choice among the many AR 15 scopes introduced in the market today. I noticed that while it suits any ACOG mount at full size, it also works great as far as durability is concerned.
It is created using the best and the highest quality materials and designed in such a way that it has a base that you can easily remove so you can use it in AR 15 optics or M16 carry handle. Another reason behind its really strong construction and design is its fog-resistant and waterproof nature.
I also think that being a reliable and compact scope makes this much easier to manage and bring on your next hunting and shooting adventures. For the reticle, it utilizes the ACSS (Advanced Combined Sighting System) CQB-M. This is one big reason behind its good and clear M4 sights.
I also noticed that this reticle is attached or fixed into a glass, making it visible even without using the illumination. I am also pleased with the inclusion of up to 11 brightness settings that include the daylight bright. These settings even increase your chance of enjoying quick acquisition when shooting at close quarters.
Another plus point of this scope is that it delivers a generous 10.16-mm exit pupil, promoting not only a forgiving eye box but also a bright and clear sight picture. Another strength is its ease of zeroing brought on by the audible and tactile ½ MOA turret clicks.
#3 Vortex Optics Strike Eagle 1-6×24 – BDC (MOA) Riflescope
If you are on a hunt for a great-performing variable magnification scope primarily designed for M4 carbine then I suggest that you include the Vortex Strike Eagle in your list of choices.
Mainly used for 3-gun competitions, you will find this riflescope valuable in all applications that put more importance on speed to target rather than the long-range tack-driving accuracy. I am happy with its zoom or variable magnification range of 1-6x as it can help promote extreme use when it comes to using it from a close range to a 600-yard distance.
I greatly appreciate the glass-etched and illuminated BDC reticle, which is also equipped with 11 illumination settings. This number of settings make it possible for the reticle to handle changing lighting conditions. It is also possible for you to store an extra battery in the included windage cap, which you can easily release.
There is also a built-in fast focus dial in the riflescope’s eyepiece, which stimulates the sharpness of the reticle all the time. It is a tough and solid riflescope designed to deal with all kinds of weather considering how fog-proof, shockproof, and waterproof it is.
Another huge plus of this riflescope is its fully multi-coated and high-quality lens, which is known for delivering a crisp and clear sight picture while also delivering an optimal performance when dealing with low lights.
The reticle also uses the second focal plane, which you can expect to stay at a similar size regardless of the magnification you use.
#4 Bushnell AR Optics Drop Zone-223 BDC Reticle Riflescope
Another scope that I encourage M4 Carbine users to use is the Bushnell AR Optics 1-4×24 Drop Zone Reticle Riflescope. This riflescope has an edge over the others because of its plenty of rewarding and exciting features. It has up to 4x magnification, which, I think, makes it capable of handling short-range tactical situations.
It also works well for a carbine or tactical rifle user. I greatly notice how it excels when used in midrange accuracy through the aid of its BDC reticle. I also like the built-in bright multi-coated optics added into the riflescope as it further makes it all the more valuable.
It utilizes high-quality materials for its exterior construction, thereby boosting its ability to offer incredible protection against a number of things plus also being long-lasting. Another great strength of this riflescope is that it promotes close quarters accuracy.
The above-average optical system combined with a turret targeting system placed in a superior aluminum housing also work in significantly enhancing the scope’s brightness. I am sure that you will also find its fast focus eyepiece very rewarding as it works in boosting both the reliability and the accuracy of the scope.
I also find pleasure in the anodized finish used in this scope as it allows the scope to have a scratchproof, fog-proof, waterproof, and rustproof construction. The fact that the turrets are easy to adjust is a strength, too.
Also, it has a protective lens cap, which many consider as a nice addition to the set.
#5 Trijicon ACOG 4 X 32 Scope Dual Illuminated Chevron .223 Ballistic Reticle
If you are searching for an ACOG (Advanced Combat Optical Gunsight) tactical scope for your M4 Carbine then you may find the ACOG 4×32 Dual Illuminated Scope from Trijicon a wise choice. Note that ACOGs are always incredible choices as these are the ones that are extensively used in the military.
I can describe this scope from Trijicon as nearly indestructible. It is primarily due to how tough it is constructed based on the shockproof, fog-proof, and waterproof coatings added to it. Constructed out of the really tough aluminum material combined with a Cerakote finish, it no longer comes as a surprise why this scope is said to be genuinely tough and solid.
Another rewarding advantage of this scope it operates without the need for a battery. It is because it is entirely illuminated through a tritium and fiber optic cable, thereby ensuring that you no longer require the use of a battery. What is good about this structure is that it further leads to increased durability, which is necessary for most survival rifles.
The reticle also works in such a way that it adjusts brightness automatically depending on the light that is presently available. It also utilizes the Bindon Aiming Concept (BAC) in its structure, which makes it possible for the illuminated reticle to aim while both your eyes are open. This promotes a superior awareness of the situation.
I am also pleased that this scope features a bullet drop compensator as this guarantees a decent accuracy when used at a long range. Furthermore, it has a limited lifetime warranty, which somehow proves its remarkable quality.
#6 Nikon P-tactical .223 3×32 Matte BDC Carbine
The P-tactical Matte BDC Carbine scope from Nikon also another product that continues to earn positive reviews from its users as it is not only high-tech but is also rugged and durable. I am greatly impressed with the versatility of its zoom ratio or range.
It has a truly flexible 3x zoom range or ratio, which works in providing a field of view found at the low end while showcasing the important detail at the high end. With this, I am sure that it is capable of satisfying the majority of the shooting demands of a wide range of hunters and shooters.
The ruggedness of this scope is also unquestionable. I am super happy with its shockproof construction as it works in shrugging of hard recoil as well as the potential damage caused by heavy and rugged use and abuse. Also, this scope is O-ring sealed, which works in preventing moisture in coming inside its body.
It is also nitrogen-purged, offering complete reliability when it is dealing with thermal shock. The fog-proof and waterproof structures of this scope for M4 are also instantly noticeable. I also find its bright and fully multi-coated lens or optics rewarding as it works in brightening all environments, even those that appear dismal.
In addition, the optic system has a rugged housing in the form of the main tube constructed from aircraft-grade aluminum. I am sure you will also love the precisely and ergonomically designed turrets. You can even use the spring-loaded knobs for windage and elevation that you can easily reset to zero once you sight it in.
This promotes ease of reference each time you need to do some field adjustments.
Best M4 Red Dot Sights Reviews of 2020
#7 Aimpoint PRO Patrol Rifle Optic
The first M4 red dot sight that I would advise using is the Aimpoint PRO Patrol Rifle optic, which is constructed ruggedly to ensure that it can handle real-world combat situations. For a police officer, this could mean bouncing along country roads or dealing with gunfights.
Due to its extremely rugged construction and its always-on structure, it is no longer surprising why it fits the needs of armed citizens, law enforcers, and the military the most. Another thing that I am sure you will also find awesome about this optic is that it is completely waterproof.
In fact, you can submerge it in up to a hundred and fifty feet deep water. With that, this optic is also a dependable choice for law enforcement marine patrols. It uses hard-anodized aluminum material for its body so the Aimpoint PRO will have a sturdy and rugged housing.
I noticed the effectiveness of this strong and solid body in protecting the electronics and glass, especially when used heavily. I also noticed the recessed front glass, which protects it from scratches. Furthermore, it is multi-coated, giving you an optimal viewing experience.
I am fond of the special band-pass coating used in the front lens, too, because this makes it appropriate for night vision devices. The optic’s 30-mm, matte black housing is also attached to a QRP2 mount, which has a torque-limiting knob, promoting quick installation and lowering the risk of over-tightening.
The Aimpoint PRO also boasts of its 1x magnification, which is actually a good thing because it means that you can use it conveniently even with your two eyes open. This promotes a complete peripheral vision and quick target acquisition.
#8 Bushnell TRS-25 Red Dot Sight
You will not also go wrong if you choose the Bushnell Trophy 1x25mm TRS-25 Red Dot Sight Riflescope. It is also another red dot sight, which is compatible with your M4. One of the many positive traits that impress me about this sight is its sturdy and durable build.
It sports a compact and small design while still being housed in sturdy metal construction. With this strength, I am quite sure that it can withstand heavy abuse and beating while still delivering excellent performance for various shooters and hunters. I am also very glad that this red dot sight from Bushnell is easy to mount.
It is also compatible for use with the majority of Picatinny rails. Furthermore, you can use it in various activities, like competitive shooting and hunting long beards. The riflescope also features an easy adjustment dial, which makes it possible for you to adjust its brightness easily based on your preference and on the present situation.
The dot of this riflescope, which is taken from a LED, which is mounted within a tube, works with up to 11 adjustments for intensity to suit various lighting situations. For its price, it can deliver excellent clarity of pictures. The glass lens can even deliver a sharp picture, which is on the same level as the costlier red dots.
It operates using a CR2032 battery. You can also enjoy the inclusion of a convenient and protective lens cap. I am also pleased that I can submerge it in water up to 10 feet in depth. This sight is waterproof, too, while having the ability to prevent it from fogging up during humid conditions.
#9 CVLIFE 1x22x33 Red Green Dot Reflex Sight
The next amazing product I am going to review is the CVLIFE 1x22x33 Red Green Dot Sight. I am in awe of how helpful this sight from CVLIFE is when it comes to shooting moving targets with a higher chance of hitting them. It is a high-quality sight that offers the kind of accuracy that most hunters and shooters are hoping for.
It is suitable for use in whatever shooting adventure you are planning to experience that requires a more enhanced accuracy. I also greatly appreciate the different green and red dot reticles included in this gun sight as it gives me the opportunity to choose my preferred target acquisition.
This leads to not only a better shooting accuracy but also a more customizable shooting experience. The amazing optical clarity that you can anticipate from this sight also ensures that you will not be bothered by whatever weather condition you are facing, whether it is the heavy rain, glaring sun, or snow.
It even has a lens with an anti-glare reflective coating, which further improves the clarity of the optics regardless of your present environmental situation. What I am fond of even more about this scope is that it has a limitless eye relief with the aid of its four reticle patterns. This also results in easy to correct parallax.
Built using the high-grade aluminum alloy material together with its anodized matte black finish, I am sure you can see right away how durable this sight is. Even when it is built with durability in mind, it is still lightweight.
Furthermore, it comes with an Allen wrench, which you can actually use in adjusting the elevation and windage effortlessly.
#10 Sig Sauer ROMEO 5 Red Dot Sight
I am also pleased with the excellent performance of the Sig Sauer 1x20mm Romeo5 2 MOA Red Dot Sight, which is why I make it a point to include this specific sight in my recommendations. One nice thing about Sig Sauer Romeo 5 that I would like to highlight is that it can offer a fantastic aiming solution for all situations.
The civilians and the armed forces can even equally use it. It has a side loading battery while promoting the quick replacement of it when needed. It also boasts of battery life of at least 5,000 hours considering the fact that this sighting system is automatically shut down when unused.
You can only activate it once it senses vibrations or movements. I like the versatility or the flexibility of this specific sight, too, which is instantly noticeable by its ability to work no matter what kind of platform you decided to mount it to. It also has a solid aluminum design, further boosting its performance and making it as long-lasting as possible.
The waterproof and fog-proof nature of the Sig Sauer Romeo5 is also impressive, making it possible to use it underwater and perform incredibly even when there is water or when the weather is foggy. I also like its ability to promote perfect visibility regardless of the condition.
It is mainly due to its ten illumination settings with eight of them suitable for daylight while the remaining two are for night vision. It also promotes an easy and quick mounting process as it suits most applications and platforms. In terms of durability, this sight also excels through its robust yet lightweight aluminum housing.
Best M4 Holographic Sights Reviews of 2020
#11 EOTECH 512 Holographic Weapon Sight
If you intend to buy a holographic sight then I suggest that you spend time getting to know more about the EOTECH 512 Holographic Weapon Sight. It is a popular holographic sight that is more appropriate for use on close range shooting. It has a simple A65 reticle but this is enough to make the optic more versatile.
I find it easy to distinguish because of its square lens and body and open design. This specific structure promotes more efficiency when it comes to seeing over the sight as it widens your field of view. This also results in better situational awareness. I like the fact that the sight is built to be neat, compact, and lightweight.
You will surely not have a tough time managing and using it. It makes use of a low-profile box for its main body containing all the electronics as well as a couple of AA batteries and a projector. It is also built to hold the highest level of protection from extreme hunting conditions.
This is made possible by its 20 brightness level that make it possible for you to get the right brightness control and clarity of vision. Pair that with good contrast and I am sure you will love using it even in conditions with low light. The simple yet attractive design of this optic also makes it effortless and easy to mount.
It is very robust and shock-absorbent. In addition, it is fully fog-proof and waterproof. In fact, it is known to be submersible by a max depth of 10 feet.
#12 Vortex Optics Razor AMG UH-1 Holographic Sight
I also find the Vortex Optics Razor AMG UH-1 Holographic Sight another amazing product that you can pair with your M4. It has plenty of fantastic and valuable features combined with its powerful and tough performance. I even love the fact that its sensitive parts are completely protected at the base.
This further showcases the sturdiness of this holographic sight from Vortex while getting rid of the need to use an obstructive secondary shroud. It utilizes a single-fused holographic element without any moving component, which is beneficial as it produces a sharp and clear image without fade or distortion.
I am also very pleased that this sight is constructed in a way that visible stray light emissions, as well as eyepiece glare, are almost eliminated. Another impressive advantage of this sight is that it utilizes a highly efficient power system, which promotes a long battery life.
It even comes with a micro USB port, which I really find useful when I am using a rechargeable battery since this means that I can charge it anytime. The fact that it appears in matte black is also a huge advance as it works in lessening the reflection of light from the optic.
I am also very glad that this holographic sight is easy to install. It is because of the integrated and quick to release mount that you can use in effortlessly installing the sight on a wide range of Picatinny or Weaver-style bases. You will also like the shockproof aluminum base, which works in protecting all the interior parts.
#13 EOTECH EXPS3 Holographic Weapon Sight
The last holographic sight that is popular for continuously delivering great performance on various situations is the EOTECH EXPS3. What I truly love about this sight is that it gives you the ability to acquire your target in a speedy manner, which offers an advantage in a number of scenarios and situations.
I discovered upon regular use that this holographic weapon sight perfectly meets the goal that all reflex sights should strive for – and that is quick target acquisition. It works in meeting such a demand by making it as versatile and sturdy as possible. I like the compactness of this sight.
Combine that with being lightweight and I am sure you will instantly find it easy to maneuver. It is compatible with shotguns, carbines, and rifles, proving its versatility. Despite being compact and lightweight, causing it to fit in just a tiny space in your weapon’s rail, it is still built with amazing technology.
In fact, it makes use of a really unique clear lens, which further improves the accuracy of your shots and the speed of your target acquisition. I am also impressed with how it is designed as it guarantees ease when it comes to mounting it. Another thing that truly caught my interest is its tough and protective build.
It is built in a way that it can withstand almost all negative scenarios and elements. In fact, it can handle a shotgun’s or a high-caliber rifle’s aggressive recoil without causing any damage to its overall accuracy.
Furthermore, it is parallax-free and boasts of several brightness adjustments that you can use for night vision and daylight.
Factors to Consider when Buying a Scope/Optic for M4
The M4 Carbine is the more compact version of the M16A2, and although it is smaller and lighter, and has an effective yet slightly short range (just above 500 yards compared to the M16’s 600 yards), it is still the better rifle. This is the primary reason why the M4 replaced the M16 in the military.
Because the M4 does have a rather long reach, but not far enough to be considered a sniper rifle, it will be much more accurate when you install a medium-range M4 carbine optic. Hitting targets that are 500 yards away is simply too difficult to do using the iron sights alone.
Here are some of the things that you need to take into consideration before buying an M4 scope:
Do you actually have a license to own an M4? In order to legally own an authentic, fully-automatic M4 carbine, you have to get a Federal Firearms License, which is basically a license to own and operate a gun store. Supposing you do have an FFL, or you are just curious about the type of M4 optics that you can use then continue reading.
Decide on its use. What will you be using the firearm for? There is no one scope on the market that is designed to do everything well. You must first decide on what you will be using the scope for. For instance, if you will be using the M4 mostly for plinking on the shooting range, then you can get a rather powerful scope. Something that can give a clear sight picture at 500 yards is fine.
The rule of thumb when choosing a rifle optic, not just M4 scopes, but for all rifles in general, is to not choose a scope with a magnification that goes well beyond the effective range of the rifle itself. For the M4, which has an effective range of a little over 500 yards, meaning there is not much bullet drop at said distance, a medium range scope with a zoom of 5-20x will do you fine.
However, do not go over 32x and definitely stay away from the long range scope selections. Keep in mind that higher zooms will need larger lenses. Also, glass is heavy so it will add quite a lot of weight to the rifle.
If you will be using the M4 mainly for hunting, you will need a scope that can handle everything that Mother Nature can throw at it. The scope should at least be purged with nitrogen or argon to make it fog-proof.
It should also be O-ring sealed at all sides to make it waterproof. It will also be good if the scope you get can handle a couple bumps and dings if you will be using it in the great outdoors.
The lenses of riflescopes need to be coated with a special film that reduces the amount of glare that the user gets and the light the lenses reflect. It also improves the lenses’ light transmission. Glare removal makes aiming your rifle easier because you do not have to deal with excess light hitting your eyes.
On the other end, it is also important that your riflescope has good anti-reflective properties because even a distant twinkling of the scope’s lens will give away your location to the prey that you have been stalking for quite a while now.
Regardless if you are out in the shooting range, or up in a blind somewhere deep in the forest, you would need a scope that can give you a clear sight picture regardless if you are in a bright area or in an environment with low lighting.
You need to find the best balance between light transmission and scope weight. The bigger the objective lens, the more light it gets. However, it also adds more weight.
Also called the crosshair, the reticle helps the shooter align his/her shot to hit the target every time. For an M4, whose effective range is just a tad over 500 yards, a basic ballistic reticle, or a high-quality yet budget red dot will be more than enough. The bullet drop at 500 yards is not that much that you need a Bullet Drop Compensation, or BDC reticle.
The M4 has a full-auto setting, so you need to mount your scope on a base that is solid and secure. This prevents the scope from losing its zero, or not too much of it at least, when you empty the magazine. Ideally, the scope mount should be one piece, which means that the base and the scope rings are milled from one piece of steel or aluminum billet.
The eye relief of a scope is the maximum distance between your eye and the eyepiece of the scope that you can get a clear sight picture. Ideally, the eye relief should be more than 4 inches because the M4 can have quite a kick when it fires. When your face is too close, the eyepiece will hit your eye socket and it might even cause serious injuries.
Frequently Asked Questions
What is a red dot scope?
A red dot scope or sight is one of the common classifications of non-magnifying reflector (also known as reflex) sight for firearms. This type of scope gives the shooter an illuminated red dot for a reticle and since it is on a fixed zoom scope usually, it is faster to acquire targets using a red dot. In addition, there is little to no parallax adjustment that you need to do even when shooting at long distances.
What is the difference between holographic and red dot reticles?
Aside from the construction and how the reticle is projected onto the lens of the scope, there are many differences between holographic and red dot sights. First of all, a holographic reticle has a wider field of vision, thanks to its rectangular window compared to the smaller, circular eyepiece of the red dot reticle scope.
Another difference between these two reticles is the size of the scope themselves. The holographic M4 carbine scopes have bigger housings because they have more parts and lenses. If you want something more low profile, you should go for red dots as it only needs room for the LED projector and the lenses.
One more difference is that the reticle of the holographic scope will not change in size when you zoom in compared to the red dot reticle where the dot also gets bigger when you zoom in on your target.
What optics does the military use of the M4?
The US Military utilizes a specially-made rifle scope for the M4 and the M16A4. It is called the Advanced Combat Optical Gunsight (ACOG) – the ACOG series of telescopic scopes for M4 that are exclusively manufactured under government contract by Trijicon. Originally, the ACOG was designed for the picatinny rail systems of the original M16 rifle, and it is modernized to also fit its successor, the M4.
The different models of the ACOG military optics for m4 provide different fixed magnification levels ranging from 1.5x up to 6x. There are also several choices in ACOG reticles. Some have both night vision illumination through an internal phosphor while others have both night vision and enhanced daytime reticle illumination through the use of a fiber optic illuminated reticle or an LED light.
The TA01, which was the first ACOG model, was released way back in 1987. Some of the ACOG models are actually designed to make use of the “Bindon Aiming Concept”, a technique developed by the founder and head optics designer of Trijicon, Glyn Bindon. This technique uses the illuminated reticle and the focusing eyepiece as a collimator sight.
This means that the shooter does not necessarily have to look through the scope. The user keeps the collimated image of the reticle in focus with the dominant eye, which the other eye is kept open to get the whole field of view so target acquisition is much faster and easier.
With this technique, the human brain will superimpose the image of the reticle on the target. Aside from having a wider field of view, this technique also makes shifting focus to the dominant eye. This solves the problem of getting a good sight picture on fast traversing targets, which is a common problem with telescopic scopes.
How to install a scope, red dot, or holographic on an M4 carbine?
First, you need to choose the kind of scope that you want to use then pick an appropriate mounting base for it. You do not simply just slap the scope on the M4 and expect it to fit perfectly. For the M4, it is highly recommended that you use a single piece design of scope base. This holds on more securely than separate base and scope rings designs.
Now that you have gathered all the necessary pieces, you can continue with the mounting process. The first thing that you need to do is to make sure that the M4 is unloaded and that there is no cartridge chambered inside. It is better to be safe rather than sorry, especially when it comes to handling firearms.
Once the rifle is rendered safe, place it on a workbench vise. Make sure that it is padded to prevent scratches on the rifle. Before you completely tighten the vise, check if the rifle is level. Do this by placing a small level on the rail.
Once the rifle is secured on the vise, get a small rag, dip it in some mineral oil, and wipe it all over the rail. Do the same with the bottom part of the scope mount. The oil will prevent rust from forming on the surfaces.
Place the scope base on the rail and check if it is at the right position. When you are happy with the placement, tighten the mounting bolts at the sides of the scope base. Tighten them just enough that they would not get jogged loose when the rifle is fired.
Once the base is locked down tight. Take off the tops of the scope rings and then place the scope into the cradle. Place the top part of the rings but do not tighten the screws fully just yet. The scope should still be able to slide inside the scope rings for now.
Take the rifle off the vise then start to adjust it for eye relief. To do this, close your eyes then hold the rifle normally. Open your eyes and see if you can get a clear sight picture from the scope. If you can, measure the distance between your dominant eye and the eyepiece. It should be far enough away that you would not get hurt when the M4 recoils after each shot.
When you are happy with the eye relief, place the rifle back on the vise, and make sure that it is once again level. This time, you need to align the reticle so that the crosshairs are perfectly vertical and horizontal in relation to the rifle.
After you are finished with all of the fine adjustments, gently take out the screws one-by-one. Place a bit of blue Loctite into each hole and replace the screws. You have successfully installed your first scope on your M4. The only thing left to do now is go to the range and zero in your scope.
If you are lucky enough to be one of the few who can legally own an M4 Carbine then you sure as heck need to make full use of it. This firearm is a masterpiece of technology but it will still make do with a scope or any kind of optical system to improve its accuracy.
One could argue that if you own an M4 Carbine then you should be skilled enough to hit targets at full range using just the iron sights. But then again, why would you not want to make target acquisition faster, and your aim significantly better by using the best scope for M4 and the most dependable M4 optics?