In April, 198, HK Company started to design a Zhong Sanjun universal submachine gun for the special forces at the request of the U.S. Naval Weapons Support Center in Crane, Indiana. Later, the development plan of this new 9mm submachine gun was also included in the light weapons development plan formulated by the General Planning Office of the U.S. Armed Forces.

The purpose of submachine gun development is to provide a universal submachine gun for all arms of the United States, especially to meet the needs of special forces in anti-terrorist operations and hostage rescue missions.

The main function of submachine guns is to "spray" bullets at the enemy at close range. Because of its light weight, small size and strong firepower, submachine guns are mainly used by heavy weapon operators, commanders, armored vehicle group members, gendarmes and other non-frontline combatants.

In the 197s, terrorist activities were very popular to take hostages in planes, buses, ships and houses, which made the anti-terrorist forces also very popular to use submachine guns. On the one hand, short weapons were operated more quickly in these narrow environments, on the other hand, there was no need to worry that the pistol bullets were too powerful to accidentally injure hostages.

compared with other similar weapons, the world-famous MP5 submachine gun was adopted by more elite troops and police in various countries. In October 1997, when Germany rescued the hijacked passenger plane of Lufthansa, and in May 198, when Britain solved the hostage incident at the Iranian embassy, it was used.

By 198, more than 5, MP5s had been equipped by many countries in the world, including France, Netherlands, Italy and the United States, etc. Moreover, in order to meet different mission requirements, these troops were equipped with all models in the MP5 series: the original size MP5A3 with telescopic stock was fast and accurate, which was suitable for general indoor combat missions;

The shooter who is the first to rush in after protecting important personnel or climbing, swimming, flying a plane or breaking a door may need to free up one hand to do other things. In this case, the MP5K with short barrel and no stock is a better choice. The theoretical firing rate of 9 rounds per minute of this 2 kg submachine gun really needs more practice, but as long as it is skilled, one hand can control it to fire automatically at close range.

MP5SD is an excellent silent submachine gun when it is necessary to reduce the acousto-optic characteristics of the muzzle to attack the target invisibly. However, is there such a three-in-one all-around submachine gun?

The purpose of p>JSSAP submachine gun development plan is to integrate the characteristics of the above three MP5 models, so that the army only needs to equip a weapon with "one gun and many functions" to meet different tactical needs, thus reducing the types of weapons, improving training efficiency, and greatly saving costs, including weapons procurement costs and training costs.

after receiving an upfront fee of about $18, from Americans, HK Company provided a sample gun named HK54A1. According to the internal naming convention of HK Company, 5 in HK54 stands for submachine gun, 4 stands for 919mm caliber ammunition (MP5 is named by the German government), and the suffix of A1 stands for the gun based on HK54 and added the technology required by JSSAP. In fact, as early as the 198s, HK Company had already started to design and test HK54A1 with its own production research fund.

in addition to the requirement of "multi-function with one gun", HK54A1 is also required to be used in all environmental conditions, from desert to polar regions. Users can carry the gun directly into battle by diving or skydiving, and the maintenance tools used can be common with the gun types currently used.

Weapons and silencers require a service life of at least 1, rounds. When shooting in all postures (upward, downward and sideways), no escaping gas will hit the shooter's face. When using the muffler, you can't see the muzzle flame or hear the mechanical sound at a distance of 3 meters from the weapon. The muffler should be reduced by at least 3 decibels. Can aim at a 1-meter portrait target with a mechanical sight in a kneeling position.

HK54A1 has many similarities with MP5SD. The gun adopts the famous roller locking system of HK company, and its caliber is 919mm (HK company proposed to the US government that HK54A1 can be converted into .45 ACP caliber if necessary). The butt of the gun is retractable, with an integral silencer, and the total weight is about 7 pounds, which is a bit reluctant for one-handed shooting. The firing mechanism can fire three shots at a firing rate of 1 rounds per minute.

the biggest feature of p>HK54A1 is that it has a pneumatic valve, which can release part of gunpowder gas to reduce the pressure in the bore and reduce the muzzle velocity of ordinary bullets to subsonic speed, so it is unnecessary to use special subsonic bombs when using the muffler.

HK54A1 can use 3 magazines or 5 drums. An auxiliary pusher handle is added, which can quietly push the bullet into the chamber. After the last shot is fired, there is an empty magazine to hang up, the magazine that can be operated on the left and right sides is stuck in the trigger guard ring, the handle of the safety/quick-release machine that can be operated by both hands is above the trigger, and the strap buckle is also conveniently turned from the left side to the right side, which is convenient for the shooter to change shooting positions.

There is a unique bolt lock on the plate unit, which can lock the bolt so that it can not be automatically circulated. This function is used to improve the noise elimination effect, but it must be filled manually. The mechanical sight has tritium light spot, which can be used at night. The hinged trigger retainer can be opened for use when wearing thick warm gloves or diving gloves. The production process of HK54A1 is the same as that of MP5, and it is mainly based on stamping and welding.

HK54A1 can't meet the requirements of all JSSAP submachine guns perfectly, but it can meet most requirements. In order to solve the technical problems, HK Company submitted the second JSSAP prototype gun named "SMG" to the US Navy Weapons Support Center in 1983.