Many of our readers might be confused with such a comparison. The argument would be that PKM and RPK are completely different weapons for different purposes. That might be so. But at the end of the day, there will be only one weapon a soldier takes to the firefight. And industry has to provide the best it can. This article is mostly a translation of the post from a different source.
Introduction to PK vs RPK argument
In the late 1960s, the Soviet Airborne Forces were armed with the 7.62 mm AKMS assault rifle and the RPKS light machine gun. Both had a folding stock and were unified to use 7.62x39mm ammunition. They were not happy with this combination, but they definitely did not want a PK in their ranks.
By 1968, the USSR had been working for over 4 years on developing a new 5.6mm rifle system (the future 5.45x39mm cartridge), which had better tactical, technical and ballistic characteristics. These would include less weight of the cartridge and guns, lower recoil momentum, higher muzzle velocity of the bullet, greater direct fire range and better accuracy, when compared to the standard 7.62x39mm rifle system. When the 5.6mm rifle was adopted by the land forces, it was obviously assumed that it would also be adopted by the Airborne Troops. However, as TsNIITOCHMASH specialists noted: "the rifle can only provide effective fire at close range (up to 600 m) and cannot provide it at greater ranges".
Analysis of the conditions for the use of small arms in the Airborne Forces
"Modern Airborne Forces, provided with air transportation means and equipped with modern combat equipment, can independently conduct large combat operations, isolated from centralized supply bases for food, logistics and ammunition. Despite the good equipment of the Airborne Forces with mechanization (infantry fighting vehicles, armored personnel carriers, etc.), the nature and degree of combat use of these means will depend in some cases on the operational purpose of the airborne assault and the geographic conditions of the landing areas. In some cases, with favorable geographic conditions for airdropping equipment (steppe, flat landscapes), airborne personnel can land with their small arms directly on infantry fighting vehicles from military transport aircraft, in other cases, with unfavorable geographic conditions (mountainous, forested, swampy, territorially limited areas, etc.), the infantry will land by parachute along with their weapons. At the same time, the landing of operational airborne troops, as a rule, will be carried out on unfortified combat positions, which, in addition, may not have natural conditions for personnel, which requires ensuring an exceptionally high combat readiness of the Airborne Forces".
These were the very words that preceded the work on the analysis of the use of machine guns in the Airborne Forces and, based on the specified conditions for the use of small arms in the Airborne Forces, the following increased and specific requirements were put forward:
Reducing the weight of the cartridge, which allows for a significant increase in the ammunition load without increasing the weight of the soldier's combat gear;
Maximum reduction in the number of types of cartridges used, which allows for maximum simplification of the combat use of weapons and the supply of units with ammunition;
A sharp reduction in the dimensions and weight of a weapon sample, which allows for a reduction in the weight of a paratrooper's combat gear and ensures the possibility and convenience of his landing by parachute;
Ensuring high combat readiness of weapons;
Ensuring high fire density;
Ensuring effective firing at all required ranges;
Ensuring high firepower at all effective firing ranges;
Maximum simplification of the operational characteristics and study of weapon samples.
An example of the maximum degree of unification of small arms models was the domestic airborne small arms system, consisting of the AKMS and RPKS. However, the military notes: “the AKM (AKMS) assault rifle in combination with the 7.62x39mm cartridge does not meet modern requirements for effective firing range. The effective firing range of the assault rifle is 400m against the required 550-600 m, and the machine gun is 600 m against the required 800m”. This was explained by the relatively low ballistic characteristics of the 7.62mm cartridge (short direct fire range - 357 m and a relatively large recoil impulse - 0.79 kg / sec).
What is surprising from the standpoint of the current state of the Airborne Forces is that the above-mentioned shortcoming was aggravated by the absence of a machine gun chambered for a rifle cartridge in the Airborne Forces' armament, which at the time of the work in question was the PK (PKS) machine gun. At the same time, the military noted at the time: "that the adoption of such a machine gun for the armament of the airborne infantry units would contradict the main requirement - the basing of the Airborne Forces small arms system on a single cartridge for all types of weapons". This was explained as follows: "the creation of a machine gun chambered for a rifle cartridge with dimensions and weight acceptable for Airborne Forces rifle units is extremely difficult and practically impossible at the present time". In addition, such a solution would still not remove the shortcomings of the machine gun chambered for the 7.62x39.
The conclusion was as follows: the low-impulse 5.6mm cartridge currently being developed in the course of the TsNIITOCHMASH R&D project, as shown by comprehensive studies and tests of this cartridge, allows for an increase in the effective firing range of the assault rifle, thus with the adoption of the 5.6mm assault rifle by the Soviet Army and, in particular, by the Airborne Forces, the preservation of the 7.62 mm RPK (RPKS) light machine gun due to its equal firing efficiency in comparison with the new 5.6mm assault rifle and another type of cartridge used, will obviously become impractical.
From the above it follows that the idea of creating a 5.6mm light machine gun unified with an assault rifle was very attractive to the military at that time.
It is worth emphasizing once again that, indeed, the new complex was being developed only as a cartridge-assault rifle combination, and the Ministry of Defense did not require light machine guns, and even unified ones.
Evaluation of the firing efficiency of machine guns using cartridges of different power
At the time of the events under consideration, the most typical type of combat was fire at rapidly maneuvering targets that appeared for a short time at various ranges, which tended to increase due to the wide dispersal of troops on the battlefield.
These features of combat tactics brought to the forefront the requirement for a significant increase in the effective firing range of small arms, both in defensive and offensive combat.
In order to determine the feasibility of setting up experimental design work on the development of a 5.6mm cartridge and weapons for it, in 1965, the troops of the Odessa Military District conducted extensive comparative tests of 5.6mm and 7.62mm models of small automatic weapons. Along with the assault rifles, machine guns chambered for cartridges of various powers (5.6mm cartridge, 7.62mm intermediate cartridge model 1943 and 7.6mm rifle cartridge) were also tested.
Firing for effectiveness from machine guns was carried out both in pairs (5.6 mm RPK and 7.62 mm RPK; 5.6 mm RPK and PK) in conditions of a defensive battle with an advancing enemy platoon, and as part of various small arms systems of a squad in conditions of a defensive and offensive battle.
The effectiveness of firing from light and company machine guns at an advancing enemy platoon
When firing from machine guns, conditions were met to ensure the comparability of the test results. For this purpose, the exercise was performed by three light machine gunners, alternating 5.6 mm and 7.62 mm RPK machine guns, and three company machine gunners, alternating 7.62 mm company PK machine guns and 5.6 mm RPK light machine guns, with each shooter repeating the firing from a machine gun of each caliber 5 times. All firing was carried out at automatic targets.
The targets represented following battlefield situations:
Target No. 1 - three machine guns at a distance of 600 m, appearing three times for 5-7 sec.
Target No. 2 - three running figures moving at a range of 600÷635 m at an angle of 45 degrees to the direction of fire at a speed of 2 m/sec over a distance of 50 m.
Target No. 3 - ten running figures at a range of 700 m, appearing twice for 20 seconds.
Target No. 4 - two anti-tank rocket launchers at a range of 800 m, appearing twice for 20 seconds.
The conclusions based on the results of the shooting:
When firing at an advancing enemy squad, the 5.6 mm RPK light machine gun is up to 2 times more effective than the 7.62mm RPK light machine gun.
Under the same firing conditions, the 5.6 mm RPK light machine gun is 1.73÷2.06 times more effective than the company 7.62mm PK machine gun.
The maximum advantage of the 5.6 mm RPK light machine gun compared to the 7.62mm RPK was obtained at a range of 600÷636 m and close to the maximum at a range of 800m.
The maximum advantage of the 5.6mm RPK light machine gun compared to the 7.62mm PK machine gun was obtained at a range of 800m and was the same and close to the maximum at other ranges.
Efficiency of firing from light and company machine guns as part of the small arms system of a squad in defense
Machine guns were fired at the following targets:
Target No. 4 - a machine gun at a distance of 400m, appearing for 10 seconds.
Target No. 6- two running figures and a rocket antitank gun at a distance of 600m, appearing twice for 10 and 30 seconds.
Target No. 9 - two running figures and a rocket antitank gun at a distance of 800m, appearing twice for 10 and 40 seconds.
In addition, machine guns fired concentrated fire at target #8 - four running figures at a distance of 700m, appearing twice for 15 seconds.
The shooting results are given in Table 3.
Table 3 | 5.6mm RPK(74) | 7.62mm RPK | 7.62mm PK |
Number of shootings | 8 | 8 | 10 |
Number of hit targets | 37 | 24 | 38 |
Median number of hit target per shooting | 4.6 | 3.0 | 3.8 |
Proportion of hit targets between 5.6mm and 7.62mm machine guns | - | 1.53 | 1.21 |
It followed from the table that the 5.6 mm light machine gun, when fired as part of a squad in defense, was 1.5 times more effective than the 7.62 mm RPK light machine gun and 1.2 times more effective than the company 7.62 mm PK machine gun.
At the same time, it was specifically stated in the report that the probability of hitting with one burst when firing from a 5.6 mm machine gun at a range of 600-800 m was 0.281-0.287, which ensured reliable destruction of living targets at these ranges and met the modern requirements for machine guns at that time.
The effectiveness of firing from light and company machine guns as part of the small arms system of a squad during an offensive on foot
During the exercise (an attack on foot), machine guns (hand-held) were fired from the positions "lying down with a bipod" and "on the move from a short stop".
Shooting was conducted at the following targets:
Target No. 4 - two waist-high figures and a rocket antitank gun appearing at a range of 500m twice for 10 and 40 seconds.
Target No. 5 - two waist-high figures and a rocket antitank gun appearing at a range of 400m twice for 10 and 40 seconds.
Concentrated fire was conducted at the following targets:
Target No. 6 - four waist-high figures and two machine guns appearing at a range of 350÷400m twice for 30 seconds.
Target No. 7 - five waist-high figures, a machine gun and a rocket-propelled anti-tank rifle, appearing for 40 seconds at a range of 500m.
Target No. 8 - six running figures, a machine gun and a rocket-propelled anti-tank rifle, appearing for 40 seconds at a range of 550m.
The firing results are shown in Table 4.
Table 4 | 5.6mm RPK(74) | 7.62mm RPK | 7.62mm PK |
Number of shootings | 8 | 8 | 12 |
Number of hit targets | 55 | 33 | 80 |
Median number of hit target per shooting | 6.9 | 4.1 | 6.7 |
Proportion of hit targets between 5.6mm and 7.62mm machine guns | - | 1.68 | 1.03 |
From Table 4 it followed that the 5.6 mm light machine gun, when fired as part of a squad small arms system in an offensive battle, is on average 1.68 times more effective than the 7.62 mm RPK light machine gun and is equivalent to the 7.62 mm PK company machine gun.
It should be noted that when firing from a 5.6 mm machine gun at a range of 400÷500 mm, the probability of hitting with one burst is 0.46÷0.69 (depending on the type of target and range), which ensured reliable destruction of living targets.
From the analysis of all the results of testing machine guns for firing efficiency, the final conclusion followed: “the use of a low-impulse 5.6 mm cartridge for a light machine gun makes it possible to significantly increase the firing efficiency in comparison with the same machine gun chambered for a 7.62 mm cartridge mod. 1943, both in offensive and defensive combat and to ensure the required range (up to 800 m inclusive) of effective shooting (with a probability of hitting with one burst of 0.25) from this type of weapon while maintaining other combat characteristics (lethal, penetrating, penetrating action of bullets, etc.). Along with the indicated advantage, the 5.6 mm light machine gun also surpasses the PK company machine gun for the 7.62 mm rifle cartridge in terms of shooting efficiency in defensive combat conditions and is equivalent to it in this characteristic in offensive combat conditions. Taking into account the lighter weight of the light machine gun in comparison with the PK machine gun, the significantly lighter weight of the 5.6 mm cartridge in comparison with the 7.62 mm rifle cartridge, which is extremely important for offensive combat.”
Taking into account all of the above, all the advantages of unification of small arms of the Airborne Forces on the basis of one cartridge, it was decided that it was necessary, subject to the adoption of the 5.6 mm assault rifle by the Airborne Forces, to create and adopt a light machine gun for the same cartridge.
The teams of design bureaus participating in the competition for a new assault rifle also developed machine guns unified with the new assault rifles. The victory was later, as we know, won by Mikhail Kalashnikov with his A-3 assault rifle and P-3 machine gun, later adopted for service under the names AK74 and RPK74, respectively, and for service with the Airborne Forces - AKS74 and RPKS74.
The information provided is not the point in the dispute whether the RPK is a machine gun or not, but in the author's opinion, it significantly adds arguments to the supporters of the Soviet Army, in which the RPK is a machine gun.
This article is taken from a different source and translated.