The history of this anti-tank gun began with work done on personal initiative in December of 1941. Before mass production and service on the front lines, the gun, indexed M-42, defeated several similar weapons in trials, including some that were easier to produce, and became the main 45 mm gun of the Red Army.
NKVD design bureaus, staffed by imprisoned engineers and designers, existed at several Soviet factories during the pre-war and wartime years. Molotov factory #172, located in the Motovilikha suburb of Molotov (modern day Perm), was no exception.
45 mm mod. 1942 gun M-42 in battle.
In early 1942, a portion of the staff of the Special Technical Bureau of the Leningrad oblast UNKVD was used to form the Special Bureau of the 4th Special Department of the NKVD at factory #172 (OKB-172 NKV USSR). N.A. Ivanov became the chief of OKB-172, and M.Yu. Tsiryulnikov became the technical supervisor. Before his arrest, Tsiryulnikov was the military representative of the GAU at factory #8, where the 45 mm mod. 1937 anti-tank gun was designed.
In late 1941, workers of the future OKB-172 worked on improving the characteristics of the 45 mm mod. 1932 19-K anti-tank gun (pre-war GAU index P-2243).
The goal was to improve penetration while retaining the existing round. This was to be done by raising the muzzle velocity from 760 m/s to 920 m/s. Muzzle velocity could be increased simply by loading more gunpowder, but that was impossible the the current barrel. An idea was pitched to install a new barrel with different ballistics onto the same mount. This would make it possible to quickly modernize all 45 mm guns in the field, and continue to use existing ammunition, replacing it with supercharged ammunition in the future.
By February 5th, 1942, the design of the new gun, called M-42 (45 mm anti-tank gun mod. 1942, GAU wartime index 52-P-243S) was finished, and presented to the management of factory #172, who approved it. All components of the 19-K would be preserved. The barrel was lengthened by 27.5 calibers, and the gunpowder charge was increased from 360 g to 395 g. In order to retain balance, the longer barrel was moved back by 150 mm, and was equipped with a heavier breech. In order for the semiautomatic mechanism to keep working with the new barrel, the mechanism's rod was lengthened, and the loop that joined the handle and rod was altered. The production of the barrel was meant to be as simple as possible. In addition to a new barrel, the M-42 had a new gun shield, thickened to 7 mm.
Blueprint of the modernized gun.
A meeting of the GAU Artillery Committee was held at the end of January of 1942 on the topic of further development of anti-tank artillery in the Red Army. As a result of the meeting, new tactical-technical requirements for the new 45 mm gun were composed. These requirements were distributed to anti-tank gun factories and design bureaus on February 4th, 1942. OKB-172 received a copy on February 13th, 1942. They suddenly remembered their initiative, not a moment too late.
On February 18th, 1942, an explanatory memo was composed on the modernization of the 45 mm gun, with calculations for the new barrel and its production, signed by OKB-172 chief Ivanov. At the same time, the factory's design bureau developed their own 45 mm gun, the M-6, which had a new simplified mount and a new barrel.
M-42 gun barrel blueprint.
On February 24th, GAU representatives at factory #172 informed the chairman of the Artillery Committee, Major-General of Artillery V.I. Hohlov, of work regarding modernization at factory #172's design bureau and OKB-172. The report mentioned that:
"...factory trials of the NKVD OKB variant are scheduled for March 10th of this year. ... The latter variant solves the issue of increasing the gun's power more quickly... The issues of increasing the power of the system and simplifying it are both solved by accepting the factory's mount and NKVD OKB's barrel. I ask for relevant instructions and a schedule of the factory trials."
On February 25th, the chief of OKB-172 wrote to the director of factory #172, A.I. Bykhovskiy, and GAU Senior Military Representative at factory #172, Lieutenant-Colonel A.N. Abramov, on the issue of the modernization of the 45 mm gun, highlighting the advantages of his variant of modernization, backed by calculations:
"Calculations prove that the mount of the 45 mm 2243A anti-tank gun allows the increase of the muzzle velocity from 760 to 900-920 m/s by simple replacement of the barrel, without needing a muzzle brake, without overloading. The calculations regarding the modernization of the 45 mm gun presented by the Special Bureau disperse all doubt and prove that the gun can be effectively modernized quite simply..."
Finally, Ivanov pointed out that the modernization surpasses the tactical-technical requirements, and can be performed very quickly. Indeed, the experimental prototype of the M-42 was built by factory #172 by March 14th, after which it went through tuning at OKB-172.
M-42 gun before factory trials.
Factory trials, consisting of towing and firing, took place from March 16th to 26th. At the same time, some components were fine-tuned for required performance and overall system reliability. The M-42 passed factory trials, in accordance with GAU requirements, and was allowed to take part in proving grounds trials.
The new "forty-fiver" goes into production
Government trials finished in early May of 1942. They included firing, barrel lifetime testing, and other parts. Due to increased pressure, the barrel lifetime was 1500 rounds, and the return spring lifespan dropped. Government trials established the ballistic qualities of the barrel: the muzzle velocity of armour piercing and high explosive shells was 885 m/s and 335 m/s respectively. Peak pressure in the barrel while firing armour piercing rounds was no greater than 2900 kg/cm².
Trials at a range of 500 meters, firing at armour with the robustness coefficient K=2400, was 59 mm at 90 degrees and 48 at 60 degrees. For the 53-K, these values were 43 mm and 35 mm, respectively.
Testing of the possibility of using the M-42's round in a stock 45 mm anti-tank gun mod. 1937 and a unified high explosive round for both guns were also proposed. The government commission's decision as a result of the trials was as follows: accept the modernized 45 mm gun into service with the Red Army, giving it the name "45 mm anti-tank gun model 1942", and begin mass production at Molotov factory #172 and factory #235.
M-42 gun breech.
Blueprints and technologies for mass production had to be worked out by June 1st, 1942. The GAU Artillery Committee had five days to approve the blueprints from factory #172. OKB-172 worked quickly, delivering the project, required blueprints, and all documentation in short time.
However, some members of the commission had a different opinion, partially caused by the state of the competitor, the M-6, which was voiced by the Chairman of the NKV Technical Council, E.A. Satel:
"Since the production schedule at factory #172 will only be ready by May 5-6th, I propose to only produce a trial batch of M-42 guns at factory #172. The size of the trial batch will be established after the factory presents production calculations."
On April 30th, 1942, before government trials were finished, the Red Army Chief of Artillery, Colonel-General of Artillery N.N. Voronov, reported to the Chairman of the State Defense Committee, I.V. Stalin, regarding the need for acceptance of a modernized 45 mm gun into service. A draft of a GKO decree was attached along with the letter, which instructed the People's Commissariat of Armament to begin production of these guns at factories #172 and #235 immediately, building 100 of each gun in May, at the cost of model 1937 guns.
Lower part of the breech.
On May 15th, a letter from Voronov arrived, addressed to the Deputy Chair of the Council of Commissars, L.P. Beria. He reported on the work performed by the Special Bureau of the 4th Special Department of the NKVD on the modernization of the anti-tank gun, the report to Stalin, and the draft GKO decree. He also asked for cooperation in launching the production of the modernized anti-tank guns as soon as possible.
After comparative trials with the M-6 45 mm gun, the M-42 was put into mass production, and a trial batch was sent into the army for field trials.
Kalinin factory gun
A new competitor for the M-42 appeared. This was a design of the Kalinin factory #8, located near Moscow: the ZIK-4 high power anti-tank gun.
In mid-July of 1942, the GAU Artillery Committee received a technical project for a new high power anti-tank gun. The project's goal was to design an anti-tank gun that was as simple as possible to produce, while maintaining and improving the combat parameters of the 53-K gun.
Thanks to the special design of the axle and trails, the ZIK-4 didn't have a lower mount. A welded pipe-like axle was used instead. The axle also contained the suspension elements. The design of the trail joints let the gun balance itself on any terrain.
Overall blueprints of the ZIK-4 gun.
The ZIK-4 had no sector gears or worm gears, and the trigger mechanism, cradle, breech, case, etc. used stamping bending, welding, and casting as much as possible. The ZIK-4 used half as many parts as the 53-K. 190 tool-hours were needed to produce a ZIK-4, compared to 450 for the 53-K and 250 for the M-6. The barrel was also radically simplified when compared to the 53-K.
Using the stock ammunition from the 53-K, the muzzle velocity of an armour piercing shell was 812 m/s (compared to 760 m/s of the mod. 1937 gun). The supercharged round from the M-42 raised that to 844 m/s. However, the Artillery Committee's conclusion, issued on August 21st, 1942, was negative.
"Considering that the ZIK-4 system is inferior to the M-42, which is already entering production, ballistically, and the simplicity of the ZIK-4 is only slightly greater than that of the M-6, and still requires work on production of a prototype, trials, and organization of new production, the 2nd Department of the Artkom considers that work on the ZIK-4 is fruitless, and that all efforts should be aimed at the production of the M-42..."
However, the project was not discarded completely.
"We consider it reasonable to borrow the breech and semiautomatic mechanism design from the ZIK-4, and apply it to the M-6 system. Install the aforementioned components on the M-6 and perform trials."
The M-42 suffered from "growing pains". For instance, the casing sometimes failed to extract when shooting with the stock 53-K rounds. This defect was resolved by altering the design of the breech. There were also attempts to use box-shaped trails, but this design showed itself poorly, and was not put into production. The only novelty that was introduced was the use of wheels without spokes, using a whole stamped disk.
The M-42, the easiest solution to improving the power of the 45 mm anti-tank gun mod. 1937, was better than several other guns, which were simpler to produce. In the end, it was the last Soviet "forty-fiver". It remained in production until the end of the war, and almost 11,000 units were made. The project supervisor, M.Yu. Tsiryulnikov, received an amnesty from Stalin on Beria's request, and had his criminal record cleared on July 18th, 1943.
M-42 gun with metallic wheels on the streets of Berlin. April 1945.
Main characteristics of the 45 mm anti-tank gun M-42 mod. 1942:
- Muzzle velocity of the supercharged HE round: 335 m/s
- Muzzle velocity of the supercharged AP round: 885 m/s
- Muzzle velocity of the regular AP round: 826 m/s
- Maximum range of the HE shell: 4670 m
- Barrel length in calibers: 69
- Number of rifling grooves: 16
- Type of rifling: constant at 7°9'45
- Depth of grooves: 0.5 mm
- Width of grooves: 6.5 mm
- Width of rifling land: 2.5 mm
- Vertical arc: -5 to +20°
- Horizontal arc: 60°
- Bore axis height: 711 mm
- Maximum length: 5043 mm
- Wheel base: 1400 mm
- Mass (combat): 570 kg
- Barrel length: 3087 mm/68.8 calibers
- System length: 4885 mm
- Rifled barrel length: 2665 mm
- Mass of the barrel and semiautomatic mechanisms: 167 kg
- Oscillating part mass: 222 kg
- Recoil elements mass: 175 kg
- Recoil length: 650-700 mm