Recoilless rifles (buildable/man portable)

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M18 recoilless rifle is a 57MM -Mp-
**7.5 cm *Leichtgeschütz 40 75MM -St- .
M20 recoilless rifle is a U.S. 75 mm caliber -St- .
3.45 inch RCL was an 88 mm British -St/Mp-? 10.5 cm Leichtgeschütz 40 -St- . 81MM Japan
37-mm automatic recoilless gun Kondakova

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57-MM, T15E13 and T15E9

75-MM, T21

105-MM, T9 and CARRIAGE, 105-MM, T9

SPG-82 / SG-82 grenade launcher
German 88 mm Raketenwerfer 43
PTR-82 Soviet anti-tank rocket launcher

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Grenade launcher RK MM / RK BM / DR

Taubin AG-2 grenade launcher

Recoilless rifles designed by Major Paloheimo

Another project by Major Erkki Paloheimo for Weapons HQ of Ordnance Department (of Finnish Armed Forces General Headquarters) was developing recoilless rifles in year 1944. The intention of this project was to develop recoilless rifle, which would be suited as infantry support weapon and capable of firing various types of projectiles. At that time the terminology concerning this type of weapon was not yet established in Finnish language, so most original documents refer to these recoilless rifles as reaktioase (“reaction weapon”). Presumably inspiration for this kind of weapon came from German panzerfaust and possibly from two Soviet Kurchevsky 76-mm DRP (Dinamo Reaktivnaya Pushka) recoilless rifles captured already during Winter War.

PICTURE: Kurchevsky’s DRP recoilless gun captured by Finnish Army during Winter War. This weapon which the Soviets had installed on a truck may have served as one of the starting points for Finnish recoilless rifle developments. (Photo taken in Sotamuseo). CLICK THUMBNAIL TO SEE LARGER PIC (62 KB).

The first prototype designed by Paloheimo was 47-mm caliber and early on referred as suppiloase (“funnel weapon”). This early prototype was tested in two test-firing events held in March of 1944. It had been designed primarily to shoot German 46-mm rifle grenades to notably longer distances than what normal rifle grenade equipment allowed, but testing proved it capable of shooting also projectiles notably larger than its caliber assuming they were first modified suitable for this purpose. Due to this work was started for developing modifications to panssaripanos m/42 (German HL-handgrenate or hafthohlladung 3), to allow it to be fired from 47-mm recoilless rifle prototype. These modifications included developing new tail and front sections which were added to panssaripanos m/42 and replacing original time fuse with impact activated concussion fuse designed to detonate the warhead when the projectile hit the target. At that time developing even larger projectiles was suggested along plan of developing “bouncing” high explosive projectile to make ammunition more lethal. While the prototype was considered a success, it was still not much more than a starting point for the development work. Variety of structural designs, barrel lengths and funnel shapes needed to be tested along testing of electrical and mechanical firing systems. Also variety of propellants was tested with type of black powder developed for ignition charges (virikeruuti) proving as best suited propellant for this purpose.

Later prototypes were all 50-mm caliber and included:

• State Rifle Factory (VKT) prototype (*): This weight 14.5-kg since it had been built to survive testing with various projectiles.
• Prototype made by Oy Wårdström: Weighting 11-kg this prototype had been designed as close as possible to intended mass-production weapon. It had 50-mm mortar barrel with area around cartridge chamber reinforced.
• “Super-durable version”: Special prototype version for pressure-testing of ammunition, weight staggering 30-kg.

(*) Documents suggest that while this prototype was originally ordered from VKT, the order may have been later transferred to Oy Wårdström, since later documents mention Wårdström-made prototype with almost similar weight (14.6-kg).

With a benefit of hindsight one can now note that at that time Finnish military made a serious mistake in developing this weapon – instead of deciding what kind of ammunition was needed and developing it, they went and attempted to adapt and modify variety of existing ammunition for this purpose. As the later events show, this turned out be serious mistake. July of 1944 above mentioned 50-mm prototypes were used for testing these projectiles:

Projectile:	Modified:
50-mm mortar shell	Unmodified
50-mm flare for mortar	Unmodified
46-mm anti-tank rifle grenade (*)	Structure reinforced, sealing ring and tail added.
Panssaripanos m/42 ()**	Installed to wooden frame developed for it.
Panssarinyrkki F1 projectile ()*	Equipped with wooden tail section reinforced with iron rings.
Smoke grenade	New tail section and weight added to pulling string.
Blinding bottle M/44	Installed to wooden frame developed for it.

(*) German 46-mm anti-tank rifle grenade. Finnish military had bought these and rifle grenade equipment already earlier.

(**) German HL-handgrenate or hafthohlladung 3. These were antitank-charges with HEAT-warheads.

(***) 100-mm German Panzerfaust klein HEAT-projectile.

Test results from tests done in June 1944 with these projectiles were considered promising and the goal was set in developing a recoilless rifle with longer range than panzerfaust and panzerschreck bought from Germany. Test results from these tests:

Projectile:	test results:
50-mm mortar shell	Good, muzzle velocities 107 - 115 m/sec.
50-mm flare for mortar	Good, burned completely before landing.
46-mm anti-tank rifle grenade	Excellent range, poor accuracy, requires development.
Panssaripanos m/42	Good, worked as intended, armor penetration untested.
Panssarinyrkki F1 projectile	Some issues but worked, 90 m range.
Smoke grenade	Good. 200 m range with 25 degree elevation. (*)
Blinding bottle M/44	Worked as intended, range 85 m.

June 1944 tests revealed that the weapon required following improvements:

• Cartridge chamber must be added to design.
• The level used for opening the weapon by turning the funnel to side must be larger and equipped with a spring.
• Firing system must be made smaller before mass-production.

Test results were so positive that already 9th of July 1944 General Major Palojärvi (Chairman of Weapons Negotiation Board) suggested for ordering field test series of 100 recoilless rifles from Oy Wårdström immediately once the weapon would have been developed ready for mass-production. However the estimates were not to remain that positive very long.

12th of August 1944 50-mm prototype of recoilless rifle was shown in presentation held in Civil Guard Officer School. Not much progress had happened since tests done in July. By that time development of the prototype representing intended mass-production weapon was still under development and it was still intended to use the same varied inventory of largely modified projectiles as before. What was to change now was that the economic considerations and questions in what way this new weapon would fit to existing inventory of weapons and what new could it offer had started to surface. It is worth noting that basically all criticism concerning the weapon was related to its ammunition – either to how poorly it suited for this purpose, how much modifications it required or due to its poor availability.

Criticism that surfaced in August of 1944 noted that:

Projectile:	criticism:
50-mm mortar shell	No real improvement over existing 50 mm mortar.
50-mm flare for mortar	Ammunition availability near zero.
46-mm anti-tank rifle grenade	Poor accuracy, massive modifications required.
Panssaripanos m/42	Difficult to use, shape does not allow long range.
Panssarinyrkki F1 projectile	Effective range not likely possible beyond 125 - 150 meters.
Panssarinyrkki F2 projectile (*)	Same basic issues as with panssarinyrkki F1 projectile.
Smoke grenade	No real improvement over existing smoke throwers.

(*) 100-mm German Panzerfaust klein projectile.

(**) 142-mm German Panzerfaust 30 HEAT-projectile.

Adaptation of 50-mm mortar ammunition for this weapon was still incomplete and due to its higher rate of fire 50-mm mortar was often actually better fire support weapon than recoilless rifle. Some hand grenades had also been modified and tested for this weapon, but they required considerable modifications and since they were not Finnish-manufactured their further availability was uncertain. When it came to German 46-mm antitank-rifle grenades, their use in recoilless rifle demanded considerable modifications to projectile and after all development work done that far, the flight characteristics of this projectile were still simply terrible. And even if the 46-mm anti-tank rifle grenade would start performing as intended, its armor penetration was just 60-mm, which was too little to be effective. Adapting modified panssaripanos M/42 antitank-charge for the purpose had proved even more difficult, since due to its aerodynamically poor shape developing it as projectile with decent flight characteristics was just impossible. When it came to <panssarinyrkki (panzerfaust) projectiles both 100-mm and 142-mm versions had been tested, but they had proved problematic. Tests suggested that effective range of 100-mm projectile from panssarikauhu F1 / panzerfaust klein could be pushed to 125 – 150 meters, but not beyond that before shooting accuracy would drop beyond acceptable level. Panssarikauhu F2 / panzerfaust 30 projectile was notably heavier and because of this required much larger propellant charge to achieve similar muzzle velocity, the propellant charge needed for reaching good range would have resulted need for having structurally stronger (read: heavier) weapon. Otherwise F2 projectile had similar limitations as with F1. In addition adapting panzerfaust projectiles to this new recoilless rifle required extensive modifications to shape and structure of the particular projectiles.

Use with smoke (hand) grenade as ammunition did not really offer anything new, which the existing smoke throwers would not been able to provide and ability to use smoke ammunition in recoilless rifle was not considered as important that it would have warranted spending much resources.

17th of August 1944 Major General Svanström (Chief of Weapons HQ) presented doubts if the concept intended for the new 50-mm recoilless rifle was flawed. He noted that for the intended role as infantry support weapon for all soldiers to use the weapon would have to be easy to learn and able to gain trust of the common soldiers, or they would be unwilling to risk their lives by using it in battle. With its variety of modified projectiles the weapon was not exactly easy to use and the ad-hoc modifications in its ammunition were not exactly inspiring confidence. He noted that while the weapon was unsuitable as infantry support weapon with various types of ammunition, but if suitable ammunition would be developed and manufactured especially for it, it could be become a successful antitank-weapon. The next day Svanström also reported to Inspector of Infantry that Major Paloheimo should be given the opportunity to complete development of his 50-mm recoilless rifle, after which the weapon should be tested for the purpose of introducing it as antitank-weapon. At the same time he suggested developing of purpose-build new ammunition intended just for this weapon.

The development work continued and 29th of August 1944 two new prototypes were tested in Mikkeli airport. These prototypes built by State Rifle Factory (VKT) and Tolvan Oy were otherwise very similar, but their lock and breech mechanisms had structural differences, which did not effect to shooting performance of the weapon. As before available ammunition was modified projectiles, which apparently were mainly used for the purpose of trying to test what kind of shooting accuracy these new prototypes were capable producing. Even with their limitations this test with 50-mm mortar shells and modified 46-mm rifle grenades suggested accuracy good enough to hit tank-size targets most of the time from 200 and 300 meters. It is not known if the plan for developing HEAT-projectile especially for this weapon ever started before Finnish recoilless rifle were terminated, or if this development work had any impact to antitank-rifles developed in Finland in 1950’s.

Major Paloheimo wasn’t alone in developing this weapon. Year 1944 he and engineer Tuomola filed patent application number 3456/44 to Finnish patent office for recoilless rifle and the venturi nozzle system used in it. Later when Finnish military awarded him with reward of 9,000 Finnish Marks for his development work with recoilless rifles, he asked the reward to be split in three parts, which were rewarded to him, engineer Saarento from State Rifle Factory and draftsmen Narinen, who had apparently made the blueprints. Finnish Armed Forces respected his wishes and rewarded the three persons each with 3,000 Marks.

It must be noted that ultimately this recoilless rifle development project produced very little results, but this was for the large part because Finnish military failed to understand early on, what would become the main use for recoilless rifles and did not start the development from recoilless rifle ammunition instead of recoiless rifle. The attempts to modify existing ordnance in such manner that it would work with the recoilless rifle showed maybe skills of improvisation, but did not produce ammunition needed to for it. Is has to be noted that apparently the Finns come up surprisingly good propellant for the purpose. The Germans used black powder as propellant in their panzerfaust recoilless rifles, last of which apparently did not achieve maximum effective range any better than the last Paloheimo’s 50-mm prototypes.

Finnish Army continued to use panzerfaust and panzerschreck until late 1950’s, at which point they were replaced with 55 S 55 (55 mm recoilless rifle model 1955) light recoilless rifle. This Finnish-developed recoilless rifle had two types of ammunition - high explosive antitank (HEAT) projectiles for antitank-work and high explosive (HEAT) ammunition soft targets. At this time it remains unknown if the prototypes developed in 1944 played any role in development of 55 S 55.

PICTURE: Finnish rocket launcher prototype installed on gun carriage of Soviet 45-mm antitank-gun getting tested. Photo taken in Tyrvää March of 1944. The series of photographs suggests that the projectile was a rocket of sort. This was likely one of the Ordnance Department prototypes. (SA-kuva photo archive, photo number 147539). CLICK THUMBNAIL TO SEE LARGER PIC (127 KB).

105 mm recoilless rifle prototype designed by Ordnance Department

(Taisteluvälineosaston 105 mm reaktioase-prototyyppi)

This was a 105-mm recoilless rifle prototype designed by Ordnance Department of Finnish Armed Forces General Headquarters. Very little is known of the prototype, since it is only mentioned in some documents. Presumably it was larger-caliber alternative designed for recoilless rifles prototypes developed by Major Paloheimo for the same organization around that time.

Reports suggest that the inspiration for this development originated from US bazooka and German panzerschreck and the development work started sometime late 1943. The apparent main goal of this development work was to develop recoilless antitank-weapon with larger effective range than panzerfaust and panzerschreck. They also reveal that first prototypes existed 21st of March 1944, but that time it was still unclear if the weapon should be a rocket launcher or recoilless rifle, so prototype of each type was under development. The recoilless rifle version prototype was to 105-mm caliber, weight 15 – 20 kg and capable firing projectile weighting 4 – 5 kg with muzzle velocity of 120 – 150 m/sec. The rocket launcher version prototype on the other hand was to be 100-mm caliber, weight 20 kg and capable firing 5 kg. However the report noted that there was development problem with propellant charge (430 grams of gunpowder) needed for rocket launcher version prototype, since the propellant was burning in uneven manner. 105-mm recoilless rifle was to be equipped with rifles barrel, while barrel to be used in 100-mm rocket-launcher prototype was to be without rifling. One of the reports mentions also 90-mm recoilless rifle prototype, which was under development in late April of 1944, but since it is not mentioned in later documents its development work probably ended before even reaching prototype stage.

By 18th of August 1944 105-mm recoilless rifle prototype had recently been completed and was about to be tested soon. Apparently the idea of 100-mm rocket launcher prototype had been abandoned by that time with development work now concentrating to 105-mm recoilless rifle prototype.

Technical specifications listed at that time:

• Caliber: 105 mm
• Weight: about 18 kg
• Muzzle velocity: 110 – 120 m/sec
• Maximum range:
• With 6 degree elevation about 200 meters
• Maximum range about 700 – 800 meters

The prototype had mechanical firing system and pressure level of about 1,000 – 1,1000 atm. It was intended to fire high explosive antitank (HEAT) projectiles with expected to have armor penetration of about 120 – 150 mm. Two sorts of ammunition had been ordered for this prototype, light and heavy version, with 50 rounds each. At that time delivery of this test ammunition was expected to happen within next 10 days. Report also noted that weight of the weapon could be probably reduced before going to next development version.

Report dating 7th of November 1944 indicates that the prototype had been tested in ballistic laboratory with the earlier mentioned two sorts of test ammunition and test results indicated that:

• Light projectile weighting 2.5-kg had muzzle velocity of 170 m/sec.
• Heavy projectile weighting 3.9-kg had muzzle velocity of 116 m/sec.

Weapon’s chamber pressure with both projectiles was about 400 kg/square centimeter. The test was considered success and the further prototypes with their weight reduced about 16-kg were to be ordered from State Rifle Factory (Valtion Kivääritehdas / VKT). Next batch of test ammunition was to be with projectiles weighting about 3.5-kg and with expected muzzle velocity of about 130 m/sec. This new ammunition prototype was about to be test-fired about two weeks later. It remains unclear if this batch of ammunition was ever tested, since apparently the whole project was probably soon stopped by Soviets in the Allied Control Commission with forced shutdown of Finnish weapons development.

Finnish military did not come up with heavy recoilless rifle until introduction of 95 S 58-61 (95 mm recoilless rifle model 1958-1661) developed in late 1950’s. This recoilless rifle equipped with both HEAT and HE ammunition have remained in use of Finnish Army to this day. It remains unclear if the prototypes developed in 1944 played any role in its development.

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47-mm low trajectory mortar M/Kahva

(47 mm laakaheitin M/Kahva)

PICTURE: Prototype of low trajectory mortar M/Kahva. (Photo taken in Sotamuseo). CLICK THUMBNAIL TO SEE LARGER PIC (68 KB).

Low trajectory mortar designed by Major Kahva for Finnish Army in year 1942 was designed for shooting vision slots of enemy bunkers and machinegun nests with 47-mm mortar shells. This shoulder fired weapon equipped with a folding adjustable bipod and used normal Mosin-Nagant rifle receiver and bolt for firing 47-mm mortar shells originally introduced for 47-mm Tampella mortar prototypes in 1930’s. Hence availability of the ammunition was not too great and while the weapon was equipped with bipod it was quite heavy and must have had considerable recoil. This weapon has simple iron sights on left side of the weapon with the rear sight loaned from M/28-30 or M/39 rifle. Sako Oy manufactured three prototypes, which were field tested, but the weapon was never approved and did not see later production.

Even if the design had not suffered the handicaps mentioned above, it had very little chance of success. Looking at the design it is fairly obvious that it was intended to fill the notch that was soon covered by recoilless rifles. Hence unfortunately the design would have become obsolete almost immediately anyway.

81-mm low-trajectory mortar m/Tampella

(81 mm kaasujarrukranaatinheitin)

Presumably intended to fire normal 81-mm mortar shells this low-trajectory equipped with recoil mechanism was developed by engineer H.O. Donner for Tampella, where he worked. Tampella manufactured prototype was tested by Finnish Army in Niinisalo test firing range, but the prototype proved less than successful. What is known the main problem was apparently with unacceptably poor shooting accuracy mainly caused by low muzzle velocity.

120-mm low-trajectory mortar m/Tampella

(120 mm kaasujarrukranaatinheitin)

Also this low-trajectory mortar was based developed by engineer H.O. Donner for Tampella during Continuation War. Tampella build at least one prototype which was tested in Niinisalo test firing range multiple times. Basically it was a 120-mm mortar barrel installed on gun carriage of captured Soviet 45-mm antitank-gun with its recoil system. The weapon was intended as possible direct fire weapon against bunkers and possibly as antitank-weapon, but proved unsuccessful. The main problems revealed by testing included gun carriage proving structurally too weak for weapon of this type and poor accuracy presumably due to low muzzle velocity. Test firing report from year 1944 also suggests that there were issues in developing properly working projectile and propellant combination.
OVERLORD'S BLOG: The First Recoilless Rifle davis. The Swedish Pansarvärnsgevär fm/42 made by the Carl Gustav company was an interesting early hybrid antitank weapon – a recoilless rifle firing solid armor-piercing projectiles. It used a 20x180mm case, propelling the 108g (1650gr) bullet at 950 m/s (3150 fps). This was capable of perforating 40mm of perpendicular armor plate at 100m (a high explosive projectile was also made). This was on the high end of armor penetration for anti-tank rifles, and the m/42 was able to do this with a weapon weighing just 11.7kg (25 lb) – less than a quarter of a comparable 20mm conventional rifle.

This was possible because of its recoilless design – upon firing, the rear end of the cartridge case would blow out and vent out the back of the weapon, instead of being firmly sealed like a conventional rifle. This created a counter balancing recoil impulse which prevented the gun and shooter from having to absorb the full recoil energy produced by a heavy bullet launching off at high velocity. The tradeoff was that much of the potential energy of firing was wasted venting out the back instead of pushing the bullet forward, which is why the cartridge case was so oversized.

About a thousand of the guns were made by the end of World War 2, at which time even it had been made quite thoroughly obsolete by the rapidly increasing thickness of tank armor. It would, however, be the stepping-stone to the m/48 Carl Gustav 84mm recoilless rifle, which used a shaped charge warhead to perforate armor with a stream of molten melt instead of relying on velocity of a hardened projectile. ChK-1M 37-mm
It was built and tested in 1945. But, it was still under development at the end of the war.
Caliber : 105 mm
EL Angle of Fire : 60 degrees
AZ Angle of Fire : -15 to +22 degrees
Shell Weight : 10.91 Kg
Shell Speed : 290 m/sec
Weight : 350kg
Range : 1,000 m

Taki

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[Suzumebachi14]

You seem to have looked at jaegerplatoon that I indicated on a topic a few weeks ago for the finnish weapons. Very good suggestions btw. I could also suggest you the Northover projector for the british.