AR-15 rifle selection

The AR-15 rifle of choice for operational shooting and reserve shooting

Why an AR-15 rifle?

If your intention is to shoot functional rifle shooting, such as SRA (Applied Reserve Shooting) or IPSC rifle shooting, the best suited tool for that is a self-loading single-action rifle equipped with loose magazines that provide sufficient cartridge capacity.

The advantages of the AR-15 or 'Arska' rifle compared to other designs are the good handling of the weapon, controllability of the recoil and accuracy. The straight line of the butt and barrel relative to each other and the relatively light moving mass of the slide and lock prevent the tendency of the barrel to rise up due to the force of the recoil. As a loading mechanism, the advantage of the direct gas system over the gas piston is that it does not cause any torsional force to the barrel. When using this type of loading mechanism, the gun's barrel can oscillate freely, thus achieving the best possible accuracy. Typically, AR-15 rifles do not lose in mechanical accuracy to bolt-action rifles.

All the main controls of the gun are accessible without changing the grip of the trigger hand. The magazine release is located on the right side of the gun above the front edge of the trigger arc and is operated by the trigger finger. The safety is located on the left side of the gun and is operated with the thumb. The gun is cocked with the support hand from the gun cocking lever, which is located in the rear part of the frame below the rear sight. If the gun is fired empty and the magazine is in place, the slide remains behind. The slide release is located on the left side of the gun and is used with the support hand. Pressing the magazine release releases the magazine from the gun and the magazine spring kicks the magazine into motion. This way, the magazine comes off the gun easily and magazine changes can be done quickly. The new magazine is put in place by pushing the magazine directly into the magazine well. Many current AR rifles have the option to use ambidextrous controls, although the price usually goes up with it. For example, the tuning lever is a very common part that is chosen to be ambidextrous.

Below is an example of Geissele's ambi charging handle:

Good handling and accuracy, as well as the possibility of customizing the weapon (modularity) have made AR-15 rifles the most popular type of weapon in competitions shot with self-loading service weapons around the world. Even in Finland, in SRA and IPSC rifle competitions today, most of the participants shoot with AR-15 type rifles.

The 5.56 Nato/.223 Rem cartridge most commonly used in AR-15 rifles is a mild-recoil and high-performance ammunition. The trajectory is straight compared to, for example, the 7.62x39 cartridge and the cartridges weigh less. The available cartridge selection is good and the price level of the cartridges is affordable compared to competing calibers.

In AR-15 rifles manufactured according to Mil-Spec standards, all parts are directly interchangeable between different brands of weapons. This makes it easier to build the gun and allows the gun to be individually equipped according to the shooter's preferences.

Choice of barrel

Due to the modular design, the AR15 can be equipped for many different purposes. One of the most essential parts of a gun is the barrel. Barrels are available in different lengths and the length of the barrel also affects the length of the gas system used. The most common rifle barrel lengths used are 14.5”, 16”, 18” and 20”. The measurements are in inches, because the AR-15 comes from the United States and there, inches are commonly used when talking about the dimensions of the weapon. Regarding the length of the barrel, it is worth noting that according to the Finnish Weapons Act, the minimum dimension of a rifle's barrel is 300mm. It corresponds to a length of 11.81" in inches, or 12 inches when rounded. It is quite common for barrels to be shortened to this minimum size. Some manufacturers have ready-made 12" barrels available, but American gun manufacturers make their guns mainly with their own domestic market in mind, which is why 12" is not very common.

The length of the barrel affects the shooting characteristics of the weapon, the weight and the accuracy that can be measured from it. A slightly longer and heavier barrel is more stable to shoot than a short one and, especially in static shooting, it is easier to hit. For those using iron sights, the long barrel enables a longer aiming distance, which also makes it easier to hit. A long barrel is also easily heavy. A barrel that is too heavy for the shooter tires the support hand when shooting with the free hand and thus makes hitting difficult. The short barrel is quick to move and the short gun is convenient to use, especially in tight spaces. In general, the choice of barrel length is some kind of compromise.

Barrels are also available with different profiles. Some are thinner than others and also lighter. A thin barrel vibrates differently than a thick one, and often a thick barrel is more accurate than a thin one, but the differences aren't necessarily big. A thin barrel heats up faster than a thick one, but it also cools down faster. Various grooves increase the outer surface area of the barrel and speed up its cooling.

The barrels are also made of different materials and with different surface treatments. US Army guns have barrels made of 4150 chrome molybdenum steel. Their inner surface is hard chrome plated and the outer surface is manganese phosphated. Such a barrel is durable and worry-free, because chrome plating protects the inner surface of the barrel from corrosion. Today, many barrels made of roaster are also sold (e.g. 416 Stainless Steel). The roaster does not necessarily need to be coated with anything, but it is not completely insensitive to rusting, so an uncoated roaster pipe should be cleaned and oiled. Some barrel manufacturers (e.g. Nordic Components or Faxon Firearms) coat their roaster barrels by nitriding. It increases the barrel's durability and provides protection against corrosion.

The price of the barrel is one of the factors that most affect the price of the entire AR-15 rifle. A high-quality barrel is accurate and durable, but even inexpensive barrels made with today's modern machines are surprisingly accurate. It is often the case that you have to spend a lot of money to achieve top accuracy, and a barrel that is just a little worse is already clearly cheaper.

The most commonly used cartridge in the AR-15 rifle is the original 223Rem / 5.56 Nato. There are several different cartridge slots for the same cartridge. The most common chamberings are 223Rem, 5.56 Nato and .223Wylde. In American guns, the .223 Rem chambering is rare because it is dangerous to fire the 5.56 Nato (5.56x45) cartridge due to the danger of overpressure. In Europe, 5.56 NATO cartridges are not sold in the same way as in the United States, so 223 Rem nesting is also used to some extent here. The 223Rem cartridge case has e.g. shorter transition cone than 5.56 NATO, which increases pressure, but also in many cases improves accuracy. 223 Wylde is the so-called a hybrid nesting often used in American racing guns. It is said to offer better accuracy than the 5.56 Nato chamber, but still allows the safe use of 5.56 Nato cartridges. The dimensions of different cartridge cases differ in many respects, so it is not easy to give an exhaustive answer about their differences and advantages over each other. 5.56 NATO is designed for military use and proven to be reliable. For racing guns, 223 Rem or 223 Wylde is a more natural option.

Below is a good video in English about the differences between 223 Rem and 5.56 Nato calibers:

 

Gas system

When the AR-15 rifle was developed, the gas system was optimized for a 20” barrel. This so-called the rifle-sized gas system is still in use, but it has been replaced by numerous other lengths. The length of the gas system affects the weapon's function, duration and recoil feel.

A pistol-sized gas system is used for very short barrels. This is used especially in the AR-15 pistols that are common in America and in addition, for example, in the 300 BLK caliber AR-15 rifles, when you want the weapon to work reliably with subsonic cartridges.

The carbine-sized gas system is used in the US Army M4 carbine with a 14.5” barrel. A carbine-sized gas system is also common in 16" barrels. Carbine gas weapons are characterized by good operational reliability, which is a result of the fact that in weapons equipped with a carbine gas system, gas usually goes to the lock even unnecessarily. In this case, the slide moves quickly, the shells fly far and the gun works even when dirty. The downside is faster breakdown of the gun's wearing parts and a sharp recoil feel. The movement speed of the slide can be restrained in the AR-15 rifle, for example, with an adjustable gas gate or by installing a heavier buffer in the gun.

Mid-length and Intermediate gas systems are located in the middle ground between carbine and rifle gases. Among them, Mid-length is more common. The Mid-Length gas system has grown in popularity in those barrel lengths where a carbine-size gas system has traditionally been used. It offers a more pleasant recoil feel, which is useful when shooting the gun for competition.

When optimizing a gun for competition use, minimizing recoil is an essential part. As for the gas system, it can be influenced by an adjustable gas gate. An adjustable gas port combined with a lightened slide, a lightened buffer, a lightened recoil spring and a powerful muzzle brake is a common combination in building a competitive competition rifle.

Rifle body

The AR-15 rifle consists of a two-part frame. The upper body, or Upper Receiver in English, is a tubular piece inside which the lock-slide combination moves. The front part of the upper frame has an external thread, where the barrel nut is tightened. The barrel of the AR-15 rifle is therefore attached to the upper frame with a barrel nut that can be tightened to the upper frame. This makes changing the barrel of an AR-15 rifle reasonably easy compared to many other rifles.

The upper frame is attached to the lower frame with two bolts. At the back of the lower frame there is a thread for attaching the stern tube. The tail pipe is positioned directly as an extension of the upper frame and contains the rifle's recoil spring and buffer. When firing, the rear of the slide of the AR-15 rifle runs inside the butt. The barrel, upper frame and butt thus form a straight line, so the recoil force of the weapon is aimed directly backwards.

The body of the Mil-Spec AR-15 rifle is forged from 7075 T6 aluminum. There are numerous manufacturers of AR-15 rifles, but there are significantly fewer forges that forge frames. Forges sell the frames as forging blanks to gunsmiths, who then finish and finish the frame. The forged frame is durable and affordable. An affordable price is achieved because the quantities to be produced are large. A more suitable manufacturing method for small series is CNC machining from an aluminum ingot. Such so-called Billet frames are available from various manufacturers, usually at a slightly higher price than forged frames. A billet frame can be made more individual than a forged frame, and they are available in many different looks.

AR-15 upper frames are also available as injection molded. In this case, the frame is usually left slightly thicker compared to the forged frame, in order to achieve the same strength as the forged frame. An injection-molded frame is usually an inexpensive and quite viable option when there is a need for an upper frame that differs slightly from a forged frame. For example, the Nordic Components Extruded Upper Receiver is like this. It has been completely omitted, which many consider unnecessary, and the forged frame includes the forward assist of the lock (Forward Assist) and the sand hatch.

AR-15 frames are also made of plastic. Modern high-quality polymer plastics are light and durable. So far, the hybrid frames of plastic and aluminum have been the most effective, because plastic is not suitable for every place. In practice, however, these plastic frames have only been popular in 22LR caliber AR-15 type weapons.

AR-15 rifle frames are also made of steel, but it is not really profitable, because steel is heavier than aluminum and does not achieve any advantage compared to aluminum in the AR-15 rifle frame. The 7075 T6 aluminum used in Mil-Spec AR-15 rifles is very strong and is excellent for gun use. Other aluminums have also been used in AR15 rifles around the world. For example, 6061 aluminum, because it is easier to machine than 7075 aluminum.

Parts that affect the ergonomics of the weapon

The parts that affect the ergonomics of the AR-15 rifle are the stock, the pistol grip and the handguard. Today, the handguard is often only slightly shorter than the barrel of the gun. A long handguard is useful in many ways. It enables a modern shooting grip, where the support hand extends quite far in front. In addition, it enables the attachment of bipods and other accessories so that there is also room for the support hand. When shooting from a stand, it offers a long support surface. When shooting, it is always better to support the gun from the handguard than from the barrel, because supporting the barrel changes the point of impact.

Traditionally, the AR-15 handguard was attached to the barrel of the rifle in addition to the barrel nut behind the gun's gas port. However, this does not allow the barrel of the weapon to vibrate freely, which affects the accuracy of the weapon. Nowadays, it is common for AR-15 rifles to only use the so-called free-float handguard. So it is a tube that is around the barrel of the gun, but does not touch the barrel from the front of the barrel nut.

It is often necessary to attach all kinds of equipment to the handguard. Because of this, they use picatinny rails, to which various accessories can be easily attached. Picatinny rails, otherwise known as 1913 rails, make the handguard easy to weigh, so the so-called negative rails. They are more holes in the handguard. So they do not increase, but on the contrary reduce weight. In the Key-mod system, the handguard has keyhole-shaped holes to which accessories are attached with a screw and its counterpart. M-LOK equipment slots are rectangular holes with rounded corners, to which equipment is also attached with screws and the corresponding counter pieces. (M-LOK, or Modular Lock, is a free licensed firearm rail locking system developed and patented by Magpul Industries). Picatinny rails can also be attached to both negative rail models, which makes mounting options more versatile.

There is a wide selection of pistol grips in different sizes and models. The size of the handle should be suitable for the size of the shooter's hand so that the trigger sits naturally halfway between the first joint of the index finger on the opposite side of the cuticle. The angle of the pistol grip affects the position of the gun hand. Especially when shooting with a short butt, the pistol grip should be at a fairly steep angle to the body of the gun, so that the shooter does not have to bend the wrist of the gun hand at an unnatural angle.

There is also a great selection of different holsters available for AR-15 rifles. The sterns are divided into fixed and teleper. Fixed sterns usually use an A2 stern tube, but there are exceptions. Tele sterns use a carbine tele stern tube, of which there are two standards; Mil-Spec and Commercial. The Mil-Spec tube is slightly thinner than the Commercial one, and thus the tail parts are also divided into Mil-Spec and Commercial tubes. In use, there is no difference between them, but when buying a new stern, you should know the type of the existing stern tube.

In the picture, the upper tail tube is Commercial sized and the lower one is Mil-Spec. The diameter of the Mil-Spec threaded part is thicker than the flat part of the pipe. In Commercial, they are the same thickness. The Commercial tailpipe is longer than the Mil-Spec, and its back is angled so that the upper surface of the pipe is longer than the lower surface. The Mil-Spec tube can be easily distinguished by the fact that its rear part is at a 90° angle in relation to the long side of the stern tube.

The advantage of the teleprop is the length adjustment of the prop, which enables the prop to be sized according to the shooter's size. The quick-adjust tail enables the tail to be sized according to the equipment or clothing in use.

Lock and slide

The lock on the AR-15 rifle is Mil-Spec made of Carpenter 158 steel. Locks made of other steels are also available, and their quality is not necessarily worse than a Mil-Spec lock. Some manufacturers advertise that they MPI test their locks. MPI (Magnetic particle inspection) testing aims to reveal possible hair breakages in the lock, which are not necessarily visible on the surface.

Different AR-15 rifle slides are available. They are usually made of 8620 steel and surface treated by phosphating. Other possible surface treatments are, for example, different nitrations, chrome plating and nickel plating. Modern surface treatments aim to achieve better corrosion resistance and reduce friction. Skates are also made of aluminum and titanium. This has been done mainly to make the skate lighter. Lightened steel slides are also available. Efforts have been made to remove all excess material from them to make the skate both light and durable. The light slide is well suited for a racing gun, where the aim is to minimize the recoil force caused by the moving parts of the gun. With a light slide, it is recommended to use an adjustable gas gate, a lightened buffer and a lightened recoil spring, so that the movement speed of the lock does not increase too much and cause malfunctions. The use of a lighter titanium teddy bear spike may also be necessary when switching to a lighter skate. As the movement speed of the lock increases, the inertial force of the teddy bear also increases. In the AR-15 rifle, the teddy bear spike has no counterspring, and the free-moving teddy bear spike may ignite the cartridge's teddy bear with just the movement force caused by the recoil spring.

Trigger mechanism

AR-15 rifles use a firing mechanism with a hammer. Its feel is somewhat different from, for example, the trigger mechanisms used in bolt-action rifles. Often the so-called the standard mechanism, i.e. the civilian mechanism that enables only single fire of the series fire mechanism intended for military use, is quite heavy and numb in its trigger feel. The standard mechanism has a rather heavy impact hammer and stiff springs to ensure reliable operation. In addition, the trigger faces are usually well crossed, so that the gun does not go off accidentally. Trigger mechanisms that feel better are available from several manufacturers. For example, Geissele also manufactures machinery for the US Army's special forces. They also have high-quality and functionally reliable launchers intended for civilian use.

Trigger mechanisms are divided into front-drive (two-stage) and non-front-drive (single-stage) mechanisms. In a front-wheel drive mechanism, the trigger first moves some distance before reaching the trigger threshold. In the mechanism without front-wheel drive, the trigger threshold is immediately at hand. In a good front-wheel drive mechanism, the shooter knows exactly when the shot is about to go off and can prepare for it by pulling the front drive. This is useful when you want to hit accurately and are not in a hurry. In the opinion of many, the mechanism without front drive is better suited for faster-paced shooting. Of course, there are opinions on this from far and wide and let everyone choose their trigger mechanism according to their own preferences.

Variations of the AR-15 rifle

Many manufacturers have tried to improve the AR-15 rifle by making changes to it. Many changes can be well justified. The downside of these variations is that they affect the availability of spare parts. For example, there is no standard for AR-15 rifles equipped with a short-stroke gas piston, and spare parts must be purchased from the manufacturer that produced the original weapon. Of course, some of the parts may be AR-15 compatible. AR-15 frames are made so that the cocking handle is moved to the side of the frame and so that the handguard is one piece with the upper frame. There are also modifications that enable a folding rear.

AR-15 rifles are also manufactured in several calibers other than 223Rem / 5.56x45. For example, AR-15 rifles firing heavy bullets in .450 Bushmaster, .458 Socom and .50 Beowulf calibers have been built for hunting. They use a modded AR15 magazine that feeds these stout cartridges from one row (single stack), while the 223Rem cartridge is fed from two rows (double stack). These calibers are designed specifically to fit the AR-15 rifle. The only difference to a 223 Rem caliber gun is the magazine, lock and barrel.

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