5 . 45×39mm The 5 . 45×39mm cartridge is a rimless bottlenecked rifle cartridge . It was introduced into service in 1974 by the Soviet Union for use with the new AK - 74 assault rifle . It gradually supplemented then largely replaced the 7 . 62×39mm round in service . History . The 5 . 45×39mm cartridge was developed in the early 1970s by a group of Soviet designers and engineers under the direction of M . Sabelnikova . Further group members were : L . I . Bulavsky , B . B . Semin , M . E . Fedorov , P . F . Sazonov , V . Volkov , V . A . Nikolaev , E . E . Zimin and P . S . Korolev . The 5 . 45×39mm is an example of an international tendency towards relatively small sized , light weight , high velocity military service cartridges . Cartridges like the 5 . 45×39mm , 5 . 56×45mm NATO and Chinese 5 . 8×42mm allow a soldier to carry more ammunition for the same weight compared to their larger and heavier predecessor cartridges and produce relatively low bolt thrust and free recoil impulse , favouring light weight arms design and automatic fire accuracy . The Soviet original military issue 5N7 cartridge variant introduced in 1974 are loaded with full metal jacket bullets that have a somewhat complex construction . The boattail projectile has a gilding - metal - clad jacket . The unhardened steel core is covered by a thin lead coating which does not fill the entire point end , leaving a hollow cavity inside the nose . The bullet is cut to length during the manufacturing process to give the correct weight . The 5N7 uses a boattail design to reduce drag and there is a small lead plug crimped in place in the base of the bullet . The lead plug , in combination with the air space at the point of the bullet , has the effect of moving the bullet ' s center of gravity to the rear ; the hollow air space also makes the bullet ' s point prone to deformation when the bullet strikes anything solid , inducing yaw . The brown - lacquered steel case is Berdan primed . Its length makes it slightly longer than the 7 . 62×39mm case which measures exactly . The primer has a copper cup and is sealed with a heavy red lacquer . The propellant charge is a ball powder with similar burning characteristics to the WC 844 powder used in 5 . 56×45mm NATO ammunition . The 5N7 cartridge weight is . Tests indicate the free recoil energy delivered by the 5 . 45×39 mm AK - 74 assault rifle is , compared to delivered by the 5 . 56×45mm NATO in the M16 assault rifle and delivered by the 7 . 62×39mm in the AKM assault rifle . Military 5 . 45×39mm ammunition was produced in the former Soviet Union , GDR and Yugoslavia , and is produced in Bulgaria , Poland and Romania . In the former Soviet Union this ammunition is produced in Russia , Kyrgyzstan , Uzbekistan and Ukraine . Cartridge dimensions . The 5 . 45×39mm has 1 . 75 ml ( 27 grains ) cartridge case capacity . 5 . 45×39mm maximum C . I . P . cartridge dimensions . Americans would define the shoulder angle at ≈ 20 . 3° . The common rifling twist rate for this cartridge is 255 mm ( 1 in 10 inches ) , 4 grooves , Ø lands = 5 . 40 mm , Ø grooves = 5 . 60 mm , land width = 2 . 60 mm and the primer type is either berdan or small rifle . According to the official C . I . P . ( Commission Internationale Permanente Pour L ' Epreuve Des Armes A Feu Portatives ) guidelines the 5 . 45×39mm case can handle up to piezo pressure . In C . I . P . regulated countries every rifle cartridge combo has to be proofed at 125 % of this maximum C . I . P . pressure to certify for sale to consumers . Wounding effects . Early ballistics tests demonstrated a pronounced tumbling effect with high speed cameras . Some Western authorities believed this bullet was designed to tumble in flesh to increase wounding potential . At the time , it was believed that yawing and cavitation of projectiles was primarily responsible for tissue damage . Martin Fackler conducted a study with an AK - 74 assault rifle using live pigs and ballistic gelatin ; " The result of our preset test indicate that the AK - 74 bullet acts in the manner expected of a full - metal - cased military ammunition - it does not deform or fragment when striking soft tissues " . Most organs and tissue were too flexible to be severely damaged by the temporary cavity effect caused by yaw and cavitation of a projectile . With the 5 . 45 mm bullet , tumbling produced a temporary cavity twice , at depths of 100 and 350 mm . This is comparable to modern 7 . 62×39mm ammunition and to ( non - fragmenting ) 5 . 56 mm ammunition . 5 . 45×39mm cartridge variants . Enhanced penetration cartridges . As body armor saw increasing use in militaries , the original 5N7 standard service cartridge bullet construction was changed several times to improve penetration . This resulted in the 7N6 , 7N10 , 7N22 and 7N24 cartridge 5 . 45×39mm variants . The 7N6 bullet has a steel rod penetrator . Since 1987 this penetrator is hardened to 60 HRC . The latter 7N6 cartridge can penetrate a 6 mm thick St3 steel plate at 300 m and 6Zh85T body armour at 80 m . 7N6 bullets have a red identification ring above the cartridge neck . The US Army ' s Ballistic Research Laboratory measured a ballistic coefficient ( G7 BC ) of 0 . 168 and form factor ( G7 " i " ) of 0 . 929 for the 7N6 projectile , which indicates good aerodynamic efficiency and external ballistic performance for the bullet diameter . The 7N10 " improved penetration " cartridge was introduced in 1992 . The size of the steel penetrator was increased to and the lead plug in front of it was discarded . In 1994 the 7N10 design was improved by filling the air space with lead . Upon impacting a hard target , soft lead is pressed sideways by the steel penetrator , tearing the jacket . The 7N10 cartridge replaced the previous variants as standard Russian service round and can penetrate a 16 mm thick St3 steel plate at 300 m and 6Zh85T body armour at 200 m . 7N10 bullets have a violet / purple identification ring above the cartridge neck . The 7N22 armour - piercing bullet , introduced in 1998 , has a sharp - pointed steel penetrator and retains the soft lead plug in the nose for jacket discarding . 7N22 bullets can be identified by their red identification ring above the cartridge neck and a black tip . The recent 7N24 " super - armor - piercing " cartridge has a penetrator made of tungsten carbide . The 7N24 round is loaded with a projectile containing a penetrator which is fired with a muzzle velocity of yielding muzzle energy . Tracer cartridges . Besides that the tracer cartridges 7T3 and 7T3M were developed . These bullets can be identified by their green marked tips . The 3 . 23 g ( 50 gr ) tracer projectile has a shorter ogival profile and for 7T3 ammunition burns out to and for 7T3M ammunition ignites at burning out to . Training and instruction cartridges . For training purposes the blank cartridge s 7H3 , 7H3M and 7Kh3 were developed . These round have a hollow white plastic imitation projectile . When these training rounds are used , the barrel of the gun is fitted at the muzzle with a Blank Fire Adapter to produce a gas pressure build - up for cycling the gun , as well as a breakup aid for their plastic projectiles . For instruction purposes the 7H4 training or dummy cartridge ( which has longitudinal grooves ) was developed . Special purpose cartridges . For special purposes the 7U1 subsonic cartridge with a black and green painted meplat and CAP cartridge for underwater were developed . The 7U1 subsonic cartridge weight is and is loaded with a projectile which is fired with a muzzle velocity of yielding muzzle energy . Accuracy of fire at ( R ) is Civil use . The 5 . 45×39mm was developed by the Soviet Union for military use and it was not intended to create civilian weapons in this chambering . Only a few civilian 5 . 45×39mm weapons were developed and commercially offered . Non AK - 74 platform rifles and commercial offerings include the East German Ssg 82 bolt action rifle and the Russian CRS - 98 " Vepr - 5 , 45 " semi - automatic carbine and Saiga semi - automatic rifle . In May 2008 the Smith & Wesson M & P15R was introduced . This was a standard AR - 15 platform rifle chambered for the 5 . 45×39mm cartridge and was Smith and Wesson ' s first AR - variant rifle in a chambering other than 5 . 56×45mm NATO and is no longer in current ( 2012 ) production . The civilian version of the Israel Weapon Industries Tavor rifle for the US market includes an optional 5 . 45×39mm conversion kit . Commercial 5 . 45×39mm ammunition . The US ammunition manufacturer Hornady produces commercial polymer - coated steel case 5 . 45×39mm ammunition loaded with polymer tipped V - MAX bullets with a stated ballistic coefficient ( G1 BC ) of 0 . 285 . WOLF Performance Ammunition offers several Berdan primed commercial 5 . 45×39mm loads . The Russian ammunition manufacturer Barnaul Cartridge Plant also offers several Berdan primed commercial sporting and hunting 5 . 45×39mm cartridges . Barnaul states that their 5 . 45×39mm cartridges produce a maximal pressure of 294 , 2 MPa ( 41 , 054 psi ) and have a bullet dispersion R of at a range of , meaning every shot of a shot group will be within a circle of the mentioned diameter at .