Yesterday's archive run was a lot more interesting than I initially expected. Not much to write home about regarding ammunition, but some particularly new information pertaining to tank destroyers and other adaptations worked on by the APX design bureau during December 1939 as well as the French fortification assault tanks.
This provisional link gathers the drawings until I properly upload all of the text:
https://drive.google.com/drive/fold...BU_w4hN8BY6?dmr=1&ec=wgc-drive-globalnav-goto
To sum up the important discoveries:
APX tank destroyer studies:
- Laffly W15 TCC (in its armored prototype), we already knew about that
- 47mm SA 39 AT gun with muzzle brake mounted on the Renault FT chassis (the Renault FT AC from World of Tanks...). Just an early draft so presumably APX was just studying every possible option, but this was rather impractical even compared to just towing the gun in position, owing to low speed, low reliability of a very old design, very limited ammo capacity (17 displayed although more could supposedly be carried if they could access the hull just below them and behind the driver), poor traverse arcs of 6° either side horizontally. Plan featured in the link. Funnily enough Puteaux mentionned that the crew compartment could be much more spacious if relocated to the rear and the engine moved to the front, which is obviously too much effort for the FT but is exacatly reminiscent of the later Marders.
- Tank destroyer using the maximum amount of elements from the Renault R35 and 47mm SA 37/39 gun. This likely referred to the 2-man turret widened R35 I found a mention of before. A prototype could be obtained in 3 months. It was noted that the design as is doesn't quite have enough armor (40mm in places but less overall) and that they must act with caution to not degrade mobility. It did have the advantage of being able to fire forward unlike the Lorraine and Laffly competitors. Overall it was deemed that the engine power of the current light tanks would not suffice and that they should either mount the gun on a new vehicle or one of the future light tank designs (AMX 39 or DAC 1) which have more engine power. This was still just with the intent of providing a tank destroyer, but at least the idea was there when the French would have to react to German developments.
Interestingly enough, the second to last option was to put the gun...on the SOMUA S35! Changing the upper armor and mounting an ARL turret then in development.
The last option was the SAu 40 with heavier armor, which more or less was the plan OTL by May 1940.
- Open top turreted tank destroyer based on the Lorraine 37 supply vehicle, using the 47mm SA 35 tank gun in a 360° turret with a 900mm diameter (presumably 1-man).
No real context, but it's a straightforward way to get a 360° 47mm SA35 on a vehicle weighing under 7 tonnes fully loaded. Plan in the link.
Adaptations:
- 240mm Long de Tranchée trench mortar mounted on the Renault FT. The chassis was found impractical for the role because it would not withstand firing of the mortar, but this paved the way to the idea of resurrecting a 1918 study for a mobile 240mm LT mortar, ideally mounted on a tracked chassis (any modern light tank would do), with the improved 1918 tube which increased range using less powder.
Other artillery
- Plan of the large 370mm howitzer designed by the Tarbes workshops and earmarked notably for the AMX self-propelled chassis, started in 1940 to throw a very large charge of 150kg of explosives at 13km or more to deal with concrete fortifications.
Fortification assault tank:
- Finally, some layout drawings of the FCM F1!
- Some more explanation on the Renault 1000 hp engine contemplated for the fortification assault tanks to replace the twin modernized Renault 12 KGM in a much smaller package. This was a V18 (!) derived from the I6 engine of the B1 Bis.
- More details on the proposed armaments. The 75mm gun with 640 m/s muzzle velocity was indeed a modified variant of the 75mm "Self-Propelled"/Char G1 gun, though the required modifications are not specified. This seems like an analogue to the 75mm M3 vs M2. The 90mm guns contemplated involved either the shortened Schneider CA 39 which threw a 11-12kg projectile at about 750 m/s, or if unavailable the naval 90mm gun firing a ca. 10kg projectile at 820 m/s. The 105mm gun adapted from the Mle 1913 field gun for the tanks indeed had an AP projectile (shell to be possibly replaced with shot) shot at 520 m/s, which could perforate a 80mm plate at extended ranges and still decent angles (33° at 50m, but still 20° at 1000m).
Finally, there was now a second 47mm design alongside the SA37/39: APX' L819 study, which was a derivative of the SA37 optimized for use in turrets thanks to shorter recoil, more convenient reloading and recuperator springs. This was the gun featured on the AMX Tracteur B and would have come in handy for any future turreted 47mm studies.
The British connection:
- additionally, the French studies of electric transmissions were being asked for by the British Mr. POTTER and F.LYDALL, the latter being a member of TOG.
- finally a reference to the French giving Char B1s in exchange for H39 castings instead of complete H39s for the British. However no deliveries could be expected until T3 1940 assuming the French kept a battalion +20% worth of production (approx 42 tanks) a month.
@Andriy777 I did rework pictures of teh Laffly armored car somewhat, here in "AM Puissantes de Cavalerie":
drive.google.com
