Heckler & Koch G3 The G3 is an assault rifle chambered in 7 . 62 . 51mm developed in the 1950s by the German armament manufacturer Heck & Koch GmbH ( H & K . ) The G3A3 ( A4 ) is a Selective - fire automatic weapon that employs a roller - delayd blowback perating system . The two - piece bolt assembly consists of a breech ( bolt head ) and bolt carrier . The bolt is held in battery by two sliding cylindrical rollers that engage locking recesses in the barrel extension . The breech is opened when both rollers are compressed inward against camming surfaces driven by the rearward pressure of the expanding gases upon the bolt head . As the rollers move inward , recoil energy is transferred to the locking piece and bolt carrier which begin to withdraw while the bolt head slowly moves rearward in relation to the bolt carrier . As the bolt carrier clears the rollers , pressure in the bore drops to a safe level , the bolt head is caught by the bolt carrier and moves to the rear as one unit , continuing the operating cycle . The bolt also features an anti - bounce mechanism that prevents the bolt from bouncing off the barrel ' s breech surface . The spring - powered claw extractor is also contained inside the bolt while the lever ejector is located inside the trigger housing ( actuated by the recoiling bolt ) . History . During the early to mid - 1950 to RFA ( West Germany ) as well as other countries of NATO had need of rearming their armies with the standard 7 . 62 x51mm cartridge . Initially Germans preferred the FN FAL Belgian , they approved the appointment G1 in 1956 . Due to obvious reasons Germany wanted to manufacture them in its own territory and tried to buy a manufacturing license from the SCA , but Belgium refused the application , so Germany turned to another project , derived from the Spanish CETME . Germany bought the manufacturing license and transferred the project to the company Heckler & Koch , located in Oberndorf , with some modifications . The draft was approved by the Bundeswehr rifle under the designation of G - 3 ( Gewehr 3 ) in 1959 , which is used from that date until 1995 by the German army , and beyond . The G - 3 and its various versions are the main weapon of more than 50 countries including : Greece , Iran , Mexico , Norway , Pakistan , Portugal , Sweden , Turkey . Over the past 40 years it has been produced in Greece , Pakistan , Iran , Turkey and Portugal . The major reason for the popularity of G - 3 rifle is that it is the construction and maintenance simpler and cheaper than its main rivals contemporaries , FN FAL and the American M - 14 . HK continued its production until the Ides of 2000 - 2001 , when she disappeared from the catalogs of the company . However , HK also produces a range of weapons that is based on the G - 3 , as the submachine HK MP - 5 Size 9mm NATO the HK33 5 . 56mm caliber , the HK - 23 and HK - 21 , 7 . 62 caliber machine guns , besides the PSG - 1 sniper rifle ( also in caliber 7 . 62 ) , among others . In general , the G - 3 rifle is one of the best 7 . 62 assault rifles in the world , he is versatile , reliable , controllable and inexpensive , and is also very popular in the civilian market , and was only produced to operate in semiautomatic known initially as HK - 41 and later as HK - 91 . The G - 3 works with the system simple delayed recoil action also known as delayed blowback , And there are two rollers that delay the opening of the breech . This system was developed at the Mauser at the end of the 2nd World War and refined in Spain . The rifle has most of its components made in pressed steel so its construction is less complicated than its contemporaries . The G - 3 is made of pressed steel almost entirely , the case of breech is made in steel plates , the grip , the trigger unit and its housing are either steel , the guard is also made in pressed steel , and in 1960 there was an update and went to make some parts of the weapon as the polymer trigger guard and trigger of the dwelling unit , these updates are called G - G - 3A3 and 3A4 . HK in 2000 through its subsidiary in Luxembourg made a version of the G3 rifle for hunting called HSG1 .