AK-74 barrel caliber: 5.45×39 mm - why this cartridge revolutionized small arms

Kalashnikov assault rifle AK-74 became a symbol of Soviet and Russian military thought, and his caliber 5.45×39 mm - one of the most discussed cartridges in the history of small arms. Developed in the 1970s as a response to the American concept of small-bore high-velocity cartridges (e.g. 5.56×45 NATO), this ammunition combined unique ballistic properties, economical production and high penetrating ability. But why exactly 5.45 mm became the standard for the Soviet army instead of the proven 7.62 mm? And how are the technical features of the barrel AK-74 affect the accuracy and accuracy of shooting?

Today we will analyze not only the history of the creation of the caliber, but also its design nuances: from the pitch of the rifling to the features of the case. You will learn how barrel length and rifling profile influence the behavior of a bullet in flight, why the 5.45×39 cartridge is considered more “humane” in comparison with 7.62×39, and what modern modifications of ammunition should be chosen for civilian weapons based on AK-74. And for carbine owners Saiga or VPO-209 We have prepared practical tips on barrel care and choosing the best cartridges.

The debate about the superiority of 5.45 mm over 7.62 mm has not subsided for half a century. Some argue that the smaller caliber provides better handling and less recoil, while others claim that 7.62mm is more reliable in extreme conditions. But the facts speak for themselves: AK-74 remains in service in more than 30 countries, and its cartridge is still being improved. Let's take a look at what makes this caliber so special.

The history of the creation of the 5.45×39 mm caliber: why the USSR abandoned 7.62 mm

Transition of the Soviet Army from the cartridge 7.62×39 mm (used in AK-47/AKM) on 5.45×39 mm in 1974 was the result of a global trend to reduce the caliber of small arms. American experience in Vietnam showed that cartridges 5.56×45 NATO (for example, for M16) provide better accuracy at long distances and less recoil, which is critical for automatic shooting.

Soviet designers led by Mikhail Kalashnikov and ballistics from TSNIITOCHMASH developed a retaliatory cartridge that was supposed to surpass Western analogues. Main tasks:

• 🔹 Increase effective fire range (up to 600–800 m versus 400–500 m for 7.62 mm).
• 🔹 Reduce ammunition weight - a soldier could carry more ammunition without compromising mobility.
• 🔹 Increase penetration ability due to the high initial velocity of the bullet (about 900 m/s versus 715 m/s for 7.62 mm).
• 🔹 Improve accuracy during automatic shooting due to lower recoil.

The first prototypes of the cartridge 5.45×39 appeared in the early 1970s, and in 1974 it was officially adopted along with AK-74. It is interesting that calibers were initially considered 5.6 mm and even 5.4 mm, but stopped at 5.45 mm as at the optimal balance between ballistics and reliability.

One of the key myths: supposedly the 5.45 mm cartridge was created as a carbon copy with 5.56 NATO. In fact, Soviet engineers went their own way - for example, a bullet 7N6 (standard for AK-74) has a steel core and an asymmetrical rear, which gives it unique properties when hitting a target.

Technical characteristics of the AK-74 barrel: rifling pitch, length and material

Trunk AK-74 is not just a tube, but a complex engineering system, where each parameter affects accuracy and reliability. Key Features:

• 📏 Barrel length: 415 mm (at AK-74M and AK-100 series). For shortened versions (for example, AKS-74U) - 206 mm.
• 🌀 Rifling pitch: 1 turn per 200 mm (1:200). This is critical for stabilizing the light 5.45mm bullet.
• 🛡️ Material: 50HFA or 50HGFA alloy steel, chrome plated to protect against corrosion and wear.
• 🔬 Rifling profile: 4 right-hand rifling with 5° bevel angle.

Why exactly step 1:200? The point is the length of the 5.45 mm bullet - it is almost 2 times longer than that of 7.62 mm, but lighter. To stabilize it, a faster rotational speed is required. If the step is taken less frequently (for example, 1:240, as with some AR-15), the bullet will begin to “tumble” at long distances. Too frequent a pitch (1:170) will increase barrel wear.

Chrome plating of the inner surface of the barrel is another know-how AK-74. It not only protects against rust, but also reduces bullet friction, extending the barrel life up to 15,000–20,000 shots (versus 10,000 for non-chromed barrels AKM).

Comparison of AK-74 and AKM barrels

Parameter	AK-74 (5.45×39)	AKM (7.62×39)
Barrel length, mm	415	415
Rifling pitch	1:200	1:240
Barrel weight, g	~950	~1000
Barrel life, shots	15 000–20 000	10 000–12 000
Initial bullet speed, m/s	900 (7N6)	715 (57-N-231)

It is important to understand that barrel length directly affects the speed of the bullet. For example, at AKS-74U with a shortened barrel (206 mm), the muzzle velocity drops to ~735 m/s, which reduces the effective fire range to 300–400 m. This is one of the reasons why the shortened versions AK-74 less accurate at long distances.

Ballistics of the 5.45×39 mm cartridge: why the bullet “somersaults” in the body

One of the most discussed properties of the cartridge 5.45×39 — its behavior when it gets into soft tissue. Bullet 7N6 (and its modernized versions, such as 7N10 or 7N22) has a unique design:

• 🔫 Steel core with an asymmetrical rear part (center of mass shifted).
• 🌀 Thin shell made of bimetal (steel + tombak), which is easily deformed.
• 💥 High speed (900 m/s) provides kinetic energy of ~1500 J at the exit from the barrel.

When the bullet hits the body, it begins precess (rotate around an axis that does not coincide with the flight path), which leads to an increase in the wound channel. This effect is often called "tumbling", although from a scientific point of view this is not entirely true. In fact, the bullet does not turn over, but begins to move in a spiral, causing more tissue damage.

For comparison: a bullet 7.62×39 (for example, 57-N-231) pierces the body almost in a straight line, leaving a neat channel. A 5.45 mm creates more extensive damage, which in some cases is considered more “humane” - the wound bleeds faster and the enemy is incapacitated.

However, there is a downside: at distances over 400 m, the 5.45 mm bullet loses speed faster than the 7.62 mm, and its destructive effect decreases. Therefore, in mountainous or wooded conditions, where shooting distances are short, AK-74 shows itself better, and in open areas (steppe, desert) the advantage may be AKM.

The myth of the "banned 5.45 mm bullet"

You can often hear that the 5.45x39mm cartridge is banned by international conventions due to its “cruelty”. In reality this is not the case. Bullet 7N6 does not violate the Hague Convention of 1899, since it has no explosive or poisonous effect. However, its design is truly optimized for maximum destructive effect, which has caused controversy.

Comparison of 5.45x39 mm and 7.62x39 mm: which is better for civilian weapons?

If you are choosing between a carabiner on a base AK-74 (for example, Saiga-5.45) and AKM (for example, VPO-208), there are several key factors to consider:

Advantages of 5.45 mm:

• 🎯 Less recoil — it’s easier to control the weapon when firing in bursts.
• 💰 Cheaper ammunition (on average 20–30% cheaper than 7.62 mm in Russia).
• 📉 Less barrel wear due to lower pressure of powder gases.
• 🏹 Better accuracy at medium distances (up to 300–400 m).

Advantages of 7.62 mm:

• 💥 Great stopping power at close distances (up to 100–150 m).
• 🌲 Better at breaking through barriers (branches, thin metal, walls).
• 🔄 More predictable trajectory at long distances (over 500 m).
• 🛡️ Less sensitive to pollution - more reliable in extreme conditions.

For hunting medium game (boar, roe deer) 7.62 mm often preferred due to the bullet's higher energy. And for sports shooting or self-defense 5.45 mm may be more convenient due to soft recoil and cheap cartridges.

⚠️ Attention: When shooting from AK-74 cartridges with a brass sleeve (for example, hunting LPS) barrel life is reduced by 15–20% due to higher friction. For long-term use, cartridges with a bimetallic sleeve are recommended.

Condition of the barrel chrome plating (no chips or rust)|Rifling pitch (should be 1:200, checked using a cartridge with a marker)|Presence of original parts (especially the bolt and receiver)|Compatibility with selected cartridges (not all 5.45 mm are suitable for civilian models)|-->

Modern modifications of the 5.45×39 mm cartridge: what to choose in 2026?

Since creation 7N6 The 5.45x39 mm cartridge has undergone several upgrades. Today the market offers options for different tasks:

Modification	Bullet type	Purpose	Features
7N6	With steel core	Standard military	Asymmetrical core, high penetration power
7N10	Reinforced core	Increased penetration (class 2 body armor)	Large bullet mass (3.6 g versus 3.4 g for 7N6)
7N22	With heat-strengthened core	For shooting at lightly armored targets	Penetrates 5 mm steel at a distance of 100 m
LPS	Lead, in a brass sleeve	Hunting/sporting	Lower speed (850 m/s), but higher accuracy
7T3	Tracer	Fire adjustment	Visible trace up to 800 m, but less accurate

For civilian weapons (for example, Saiga-5.45 or VPO-209) the most popular:

• 🎯 LPS - for accurate shooting at distances up to 300 m.
• 💥 7N6 - for self-defense (but requires permission to carry).
• 🔫 Training cartridges (with a plastic bullet) - for training at close ranges.

When choosing cartridges, pay attention to production batch. For example, cartridges 7N6 releases from the 1980s and 1990s may have more consistent performance than modern ones (due to changes in propellant technology).

⚠️ Attention: Cartridges with an armor-piercing core (7N10, 7N22) are prohibited for civil circulation in most countries, including Russia. Their use outside military service is punishable by law.

AK-74 barrel care: how to extend its life and maintain accuracy

Trunk AK-74 with proper care it can last for decades, but there are a few critical points:

• 🧹 Cleaning after shooting - required, even if the barrel is chrome-plated. Residues of gunpowder and copper corrode the metal over time.
• 💧 Lubrication - use special weapon oils (for example, Ballistol or LPX).
• 🔧 Checking the rifling — once every 5,000 shots, inspect the barrel for wear (you can use boron-kaina or endoscope).
• 🔥 Avoid overheating — prolonged automatic shooting (more than 30 shots in a row) reduces the service life of the barrel.

For cleaning the barrel AK-74 you will need:

1. Cleaning rod with bronze brush.
2. Lint-free rags.
3. Carbon solvent (for example, Hoppe's No. 9).
4. Anti-corrosion oil.

Cleaning process:

1. Disassemble the weapon and remove the barrel (if the model allows it).
2. Soak the brush in solvent and go over the cuts 10–15 times.
3. Wipe the barrel with a rag until the carbon deposits are completely removed.
4. Apply a thin layer of oil.

Pay special attention transition of the chamber into the barrel — This is where the most soot accumulates. If this area is not cleaned, then after 2-3 thousand shots, erosion of the metal may begin, which will lead to a decrease in accuracy.

Modernizing the AK-74: is it worth changing the barrel or caliber?

Many owners AK-74 are thinking about modernization - for example, replacing the barrel with a longer one (for sniper variants) or converting it to a different caliber (for example, .223 Remington). But there are several pitfalls here:

Upgrade options:

• 🔧 Replacing the barrel with a longer one (for example 550 mm for SVD- similar options). This will increase the muzzle velocity, but will require modifications to the gas system.
• 🌀 Installing a barrel with a different rifling pitch (for example, 1:170 for shooting heavy bullets). Risky - accuracy may deteriorate.
• 💥 Conversion to 5.56 NATO. Theoretically possible, but will require replacement of the bolt, receiver and magazines. In fact, it will no longer be AK-74, but a hybrid.

Before making any modifications, please note:

• ⚖️ Legal restrictions — in Russia, unauthorized modification of weapons is prohibited (Article 223 of the Criminal Code of the Russian Federation).
• 💰 Cost - high-quality barrel for AK-74 will cost 15–30 thousand rubles, plus the work of a gunsmith.
• 🎯 Result - is not always justified. For example, lengthening the barrel by 100 mm will increase the bullet speed by only 3–5%.

If your goal is to improve accuracy, it is better to pay attention to:

• 🔫 Trigger tuning (reducing backlash).
• 👁️ Installation of a high-quality sight (for example, Software 4×24 or Vortex Crossfire).
• 💎 Use-match ammo (for example, LPS with selected bullets).

FAQ: Frequently asked questions about the 5.45×39 mm caliber and the AK-74 barrel

Can an AK-74 be fired with 5.56 NATO ammunition?

No, absolutely not. Despite the similar caliber, the cartridges 5.56×45 NATO have a different pressure, case and bullet shape. Shooting them out AK-74 will lead to rupture of the cartridge case, damage to the bolt and possible injury to the shooter. The only safe option is to use adapters, but this will reduce reliability and accuracy.

What is the service life of the AK-74 barrel when firing 7N6 cartridges?

With proper care, chrome-plated barrel AK-74 withstands 15,000–20,000 shots cartridges 7N6. However, the resource depends on:

• The quality of the cartridges (a bimetallic sleeve wears out the barrel less than a brass one).
• Firing mode (constant bursts reduce resource by 1.5–2 times).
• Maintenance (irregular cleaning accelerates erosion of rifling).

After 10,000 shots, it is recommended to check the barrel for wear using calibrator caliber.

What is the difference between the AK-74 barrel and the AK-12 barrel?

AK-12 uses the same cartridge 5.45×39 mm, but its barrel has several improvements:

• More precise chrome plating (technology "chrome-ceramic").
• Improved chamber geometry for reliable chambering of cartridges.
• Tighter tolerances during production (less variation in accuracy between copies).

However, the rifling pitch and barrel length remained the same (1:200 and 415 mm, respectively).

Is it possible to use an AK-74 barrel for homemade weapons?

In Russia, the manufacture of firearms without a license is prohibited (Article 223 of the Criminal Code of the Russian Federation). Even if you have a legal gun from AK-74, its installation in a homemade structure is equivalent to the illegal manufacture of weapons. An exception is the registration of weapons with the Russian Guard as homemade with obtaining permission, which is extremely difficult in practice.

Which 5.45x39mm cartridges are best for hunting?

For hunting medium game (boar, roe deer) the following are suitable:

• LPS - lead bullet with good stopping power at distances up to 200 m.
• Expansive cartridges (for example, SP-5 or SP-6) - expand when hit, but require permission.

To shoot at a bird or small animal, you can use cartridges with a lightweight bullet (for example, UCH-5.45 with a plastic bullet).