French antitank weapon projects before June 1940

[Elan Vital]

Hi everyone,

Just like my previous threads in the same section, talking about French antitank weapon projects in development in the interwar period or up to 1940 that didn't get to enter service, based on my archive findings. I'm gonna start with the ones that caught me completetely off-guard:

New 37mm towed antitank gun for 1941 (translation of part of a wartime report, probably in 1940):

"It was to be expected that the 25mm antitank gun would become, in 1941, powerless against the tanks reported to be under development by the enemy. The 47mm gun being too heavy for its use in the Infantry branch (author's note: operated by the Artillery), the APX designed a 37mm gun with the same interior dimensions as the 37mm of the model for the Fortified Regions (the 37 AC 34), on a conventional two-legged carriage (the novelty was a reduction in weight by incorporating the gunshield in the carriage's construction).

3 prototypes were ordered in May 1940."

Comparative caracteristics:​

25 mle.1934​	47mm mle.1937​	Proposed 37mm​
Weight (kg)​	480​	1070​	550​
Length (m)​	3.2​	4.1​	3.5​
Width (m)​	1.05​	1.62​	1.15​
Perforation capability (cemented steel, angles from vertical)​	40mm @400m @30° 20mm @800m @23°​	60mm @400m @35° 60mm @800m @24°​	50mm @400m @30° 50mm @800m @20°​

The 37mm AC 34 which this gun was based on was a 37mm L50 casemate gun which was itself based on the naval mle.1925 AA gun, firing a 790-900g solid shot APCBC projectile at anywhere from 800 to 890 m/s (850-860 too, sources don't agree) in a necked 277R case.

The proposed gun can be seen as a near direct analogue to the British 2 pdr when using supercharged APCBC ammunition (1942-1943), but in 1941 and on a conventional light carriage. Owing to the possibly slightly higher muzzle energy and APCBC construction of the projectile, this gun wouldn't have faced the issues the 2pdr historically had against 50mm face hardened and 30+30 spaced armor arrangements on German tanks in 1941. As can be seen in the table, this gun could defeat the spaced plate at more than 800m from dead on, and still at decent ranges even if the tank was engaged from some limited side angle.

The 37mm was seen as a 25mm replacement and was not much heavier than the mle.1934, which was a little heavy for the infantry but still acceptable*, while being half the weight of the 47mm AT gun (and additionally smaller, which would have made it easier to hide).

*By 1940 the mle.1934 was replaced in production by the very lightweight mle.1937 (which couldn't be towed at high speed) and the mle.1934 modifié 1939 which was of intermediate weight between the former two but could be towed at high speeds.

Powerful antitank materiels (letter from 1st of May 1940 by General Armament Engineer Lemoine):

"In the letter n°7 S/C-18 from January 8, 1940, the General Inspector of Studies and Technical Experiments of the Ground Army requested the realisation of a prototype of platform for powerful antitank 75mm mle.1908 and 90mm guns, along the lines of the early projects which had been submitted to him by the Weapon Studies Inspection.

The study of a mobile platform and its construction are being finished at the Vincennes construction workshop. A 75mm mle.1908 gun lent by the Naval department is currently being mounted on this platform. A Renault AMC 35 cavalry tank (armored car) has been provided as the armored prime mover to be associated to this materiel.

The materiel will be completed and trials will start at the end of May.

Moreover, the Tarbes construction workshop studies an oscillating mass for a powerful 90mm gun (ballistics of the 90mm CA 39 Schneider AA gun) which can be mounted on the same platform.

The undergoing realisations correspond to the following considerations:

1° - Power:

The 75mm mle.1908, firing capped solid shot in special steel at the muzzle velocity of 850 m/s should penetrate 108mm of special steel at 500m at 30°.

The 90mm gun firing the same kind of projectile at 830 m/s could perforate 125mm under similar conditions, which could be further increased if we adopted a subcaliber 90/75mm projectile.

2° - Requirements:

An antitank materiel should meet the following requirements:

Offroad mobility
Quick deployment in and out of battery
Wide firing arc
Quick change of targets over a large front
Good personel protection
Ability to engage moving targets

The best solution would be to use an armored self-propelled gun mounted on tracks, but such a vehicle, a real powerful combat tank, would be very slow to make under the current circumstances.

The materiel currently in construction would be a less perfect solution but which meets most requirements and would be much quicker to make in any case.

Organisation of the antitank materiel:

The materiel is organised to fire without being separated from the prime mover. This particularity somewhat allows the deletion of deployment maneuvers in and out of battery, always critical when under fire. Changes of targets or position are easy and quick. The prime mover contributes to stability when firing owing to its mass.

Prime mover:

As indicated, the tractor for the prototype materiel is an AMC 35 Renault armored car, but nothing imposes the choice of this model. The tractor just needs to be capable of towing in rough terrain, be armored, that its weight is suitable for the gun's power and that it can carry ammunition.

Artillery materiel:

The platform and prime mover are linked through a robust universal joint allowing the assembly to bend itself in the horizontal plane when steering, or in the vertical plane to cross an obstacle or change slopes. On the contrary, the articulation prevents the platform from turning along its longitudinal axis when the prime mover is static.
On the opposite end, the platform stands on an axle which can oscillate in the vertical plane, allowing the wheels to follow the shape of the terrain.
The mount, fixed on the platform is of the pivot type, allowing a lateral firing arc of 40 to 50°. Vertical traverse angles go from roughly -5 to +12°.

Anchoring:

As the gun is meant to fire up to 25° either side of the platform's axis, it is necessary to anchor it to the ground to prevent the wheels from sliding laterally when the shot is fired.
A chassis, articulated on one end to an axis parallel to the axle holds at its other extrexmity a plate reinforced with angles and equipped with small spades disposed in parallel to the platform's axis.
When the gun is put in battery, the chassis is disconnected, falls under its own weight and just needs to reverse for 0.5m so that the spades dig into the ground and prevent any lateral movement.

The gun has no particularly. Its semi-automatic breech allows one crew member to be deleted. It is fitted with a muzzle brake with side vents to reduce recoiling effort by 40%. The materiel is completed with large surrounding shields. Two seats are placed on the anterior face of the shields.

Service of the piece:

The crew includes:
- a commander
- a driver
- a gunner
- a loader
- an assistant loader

When moving, the first three are mounted on the prime mover, the other two on the shield's seats (like the German 77mm). Maneuver to put the gun in battery consists in orienting the platform's axis in the direction of the target or the zone to watch over.
Changing targets is done the same way, the tractor steering in the correct direction and the crew slightly raising the spades during this time.
The commander stays in the tractor's turret and directs movement.
Fire execution features no particularity.
The aiming components for the 75mm mle.1908 gun are suitable for easy aiming on moving targets. Those of the 90mm gun will be designed for the same role."

This was pretty much a stopgap self-propelled gun of extreme power for the time with greater mobility and ease of deployment than a conventional towed gun. The 90mm gun is a close ballistic analogue to the US 90mm M3 and the 75mm is of analogue power to the British 75mm HV meant for tanks (with the 6.4kg projectile compatible with all 75mm mle.97 pattern guns).





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[Elan Vital]

Light infantry antitank weapon (squeezebore):

"The current concern of Command is to ensure the antitank defense of the forwardmost infantry echelon, that is the company's combat echelon in contact with the enemy.

Defense against tanks in first line is currently achieved by 25mm guns of the C.A.B (antitank companies of the battalions) which are employed following firing plans of the battalions and thus aim to ensure the integrity of the position following the idea of maneuver of command, without necessarily aiming to protect the complete combat echelon.

The latter will thus be often partially crushed by enemy tanks and it means either: accepting systematically high losses or being forced to retreat the echelon which, if not prepared, will lead to losses or disorder.

It is thus of importance to give a self-defence antitank weapon to these first line elements.

This weapon must be light enough to be brought in by people (as the transport vehicle generally can't arrive in first line) and sufficiently powerful to protect these forward elements against infantry support tanks.

This system should in our opinion be able to perforate 40mm of armor at 30° at 250m. This close range being the maximum range the 25mm gun can perforate 40mm at 30°.

The current solutions of improved 37mm SA 16 gun (1) and Boys rifle (2) are only stopgaps, though absolutely necessary.

We must thus seek a new weapon as powerful as the 25mm gun, within the range specified above, but lighter and that can be split in unitary loads suspectible to be carried or trained by a single man, so lighter than 40kg, and of such volume as to be able to go inside trenches and holes.

As a simple advice:
1) The easiest solution would be a split weapon made using the existing 25mm tube, which would allow us to retain the existing tube and ammo.
2) Another solution would be Larsen type guns, but we would need to know the results of the trials at Puteaux and Tulle.
3) Finally we can maybe expect the creation of a weapon that is lighter yet more powerful than the 25mm mle.1937 thanks to technical progress.

This seems to be the real solution to the problem considering the tanks that will be facing us when this weapon is delivered to our troops.

(1) Of insufficient power (40mm at 20° at 100m) and which currently exists in limited numbers (1100 as replacements for the 25mm gun at this echelon)
(2) Which has the power of a 13.2mm machinegun, and we ignore the amount we could obtain from the British."

28th of January 1940: Light antitank conical bore weapon

The TULLE arsenal has realized a light weapon which could potentially be the antitank weapon for forward elements requested by the Commander in Chief.
Given the delays imposed for the completion of this study, it was necessary to use existing or known elements for the weapon, ammunition and carriage. Moreover the search for sufficient penetration did not allow us to envision a shoulder weapon and imposed its use on a carriage.

II - Characteristics

Weighing 72 kg and having a length of 2.5m, this prototype can be split in two loads:
- one containing the oscillating mass and mount weighing 48 kg (to be modified to be split in 2 24kg loads)
- the other including the carriage (the carriage of the Hotchkiss machinegun), weighing 24kg.

With an initial caliber of 20mmn the weapon uses a conical muzzle which can be:
- 20/16mm caliber to accelerate the projectile to 1450 m/s at the muzzle
- 20/14mm caliber to achieve 1700 m/s MV.

The perforation obtained in these conditions by the APCNR projectile is 30mm at 100m at 25 to 30°. The weapon can shoot in semi-automatic or automatic modes and is loaded with a 10-round vertical magazine.
The Hotchkiss machinegun carriage used has been fitted with a device to improve traverse speed.

III- Opinions

The weapon is sturdy, accurate, easy to produce, can be split in 3 24kg loads and is an antitank materiel with double the penetration power of the Boys rifle and susceptible to be easily carried to forward positions.
In this form the materiel and ammunition do not constitute the ideal weapon. Perforation could be notably improved with a new projectile* and could reach 35 to 40mm at 100m. A special carriage could notably improve ease of use of the gun.
But if we want to obtain this weapon quickly we must take it in its current form and its ammunition.
In these conditions we could obtain 1000 guns by the 1st of May under the following conditions:

1/ Without assuming the decision to adopt the gun which could be done in February following its presentation to command, it would be necessary to obtain the approval from the Air Ministry for the production of 1000 20mm gun blanks (author's note: I suspect they used Hispano Suiza 404/Oerlikon tooling).
2/ The necessary timeline for the installation of serial production tooling was incompatible with the envisionned date; invite the Armament Ministry to study the possibility of production in the Central Workshops of the various Establishments.
The study of serial production would be undertaken simultaneously.

*The current projectile is of semi-soft steel. A projectile with hard steel core and soft metal fins would be significantly superior but it is not yet ready and would induce long delays.