Categories
WW2 Italian SPG Prototypes

Autocannone da 75/32 su Autocarro Semicingolato FIAT 727

Kingdom of Italy (1943)
Half-Track Mounted Self-Propelled Gun – Paper Project

The Autocannone da 75/32 su Autocarro Semicingolato FIAT 727 was an Italian anti-tank self-propelled gun designed in 1943 based on the FIAT 727 half-track chassis for the needs of the Italian Regio Esercito (English: Royal Army).

The delays with the production of the FIAT 727 caused the delay of the half-track Autocannone. The project was canceled after the 8th September 1943 Italian Armistice.

In Italian, Autocannone da 75/32 su Autocarro Semicingolato FIAT 727 literally means Truck-mounted 75 mm L.32 cannon on FIAT 727 half-track hull.

Italian Half-Tracks

Before the Second World War, the Italian Army and the Italian industry were not interested in half-tracked vehicles, besides some interwar projects, such as the Semicingolato Corni (1923). The Italians preferred heavy-duty trucks or medium trucks with all-wheel drive. With the start of the conflict, during the French campaign, Italian officers were impressed by the mobility of the German half-tracked vehicles, such as the Sd.Kfz.7 heavy-duty half-track or the medium Sd.Kfz.10 that were used by the Wehrmacht to tow artillery pieces and ammunition.

An Sd.Kfz.10 of the Wehrmacht in the Soviet Union in June 1941. Source: wikipedia.org

In 1940, Colonel Sergio Berlese, an Italian designer in the Servizio Tecnico di Artiglieria (English: Artillery Technical Service), visited various German military vehicle production plants. In the production plant at Kiel, he was impressed by the German armed half-tracks and returned to the Kingdom of Italy, suggesting to his commanders that similar vehicles be produced in Italy. He easily managed to gain interest from the High Command of the Regio Esercito, and some generals showed some positive opinions towards the production of half-tracks in Italy.

Col. Berlese planned to create an Italian armed half-track, even if at that time, Italy was not producing half-tracks.

The Regio Esercito’s General Staff, enthusiastic about Col. Berlese’s ideas, ordered him to develop his design on the chassis of a fully tracked vehicle. This decision was made to speed up the project. If it was necessary to wait for the production of a half-track chassis to create a self-propelled gun on it, it would have taken a great deal of time that the Regio Esercito did not have.

This led to two different design paths. Under the supervision of Col. Berlese, an artillery piece was mounted on a fully tracked chassis. This was the Semovente M40 da 75/18, one of the most successful vehicles of the Regio Esercito during the war and the only successful design of Col. Berlese.

The other design path led the Italian Army High Command to put out some requests for the creation of half-tracks in 1941. The first developments were presented in the same year by the Centro Studi ed Esperienze della Motorizzazione (English: Vehicle Study and Experience Center) in Rome. These were the Bianchi Mediolanum medium trucks modified with tracks and the heavy duty Alfa Romeo 800RE (‘R.E.’ stands for Regio Esercito) truck.

The Alfa Romeo 800 CSEM semicingolato. Source: wikipedia.org

These two vehicles, which were tested by Italian Army specialists, were standard medium trucks with modifications to the rear axles. They did not give the desired results in off-road tests and towing tests and were abandoned.

Bianchi Mediolanum in half-track configuration during testing. On the tarpaulin is the writing R. Esercito. Source: wikiwand.com

In 1941, the Regio Esercito High Command asked for an Sd.Kfz.7 from the Wehrmacht. The German Army responded positively and, during the same year, a German half-track was tested at the Centro Studi della Motorizzazione (English: Center for Motorisation Studies) in Rome, impressing the Italian officers with its towing capabilities and robustness.

Almost immediately, the possibility of producing the half-track under license was requested, but some bureaucratic problems slowed the release of documents. Production of the suspension and tracks was only granted by the German manufacturer Krauss-Maffei in 1942.

The production of the Italian copy of the Sd.Kfz.7, called Autocarro Semicingolato (English: Half-tracked Truck) Breda 61 (also known as the ‘Breda 8t’ for its weight), and a smaller version produced by FIAT called FIAT 727 or Maffei-FIAT 727 (a copy of the Sd.Kfz.10), started very slowly.

The Autocarro Semicingolato Breda 61 da 8 t during testing. Source: panzerdb.com

The FIAT 727 prototype was tested by the Italian Regio Esercito in 1943 at the Centro Studi della Motorizzazione (English: Center for Motorisation Studies) in Rome. Before the 8th September 1943 Armistice, a total of 6 or 8 pre-series vehicles were produced by the FIAT plants of Turin. It was planned to deliver the first vehicles in 1944, but the Germans were not interested in producing such medium half-tracks and the project was abandoned.

The Maffei-FIAT 727 half-track. Source: Semicingolati, Motoveicoli e Veicoli Speciali del Regio Esercito Italiano 1919-1943

Like in the case of the Breda 61, even while the FIAT 727 was just a paper project, way before the production of a prototype, a team of engineers started the development of variants on its chassis: the Autocannone da 75/32 su Autocarro Semicingolato FIAT 727 and the Autocannone da 40/56 su Autocarro Semicingolato FIAT 727.

Design

The only source that mentions the Autocannone da 75/32 su Autocarro Semicingolato FIAT 727 is the book Andare Contro i Carri Armati written by Filippo Cappellano and Nicola Pignato. The two authors dedicated very few words to the vehicle and no kind of blueprint even exists.

Autocarro Semicingolato Maffei-FIAT 727 da 3 t

After testing the Sd.Kfz.7 in 1941, FIAT and Breda divided the tasks. FIAT would produce a scaled-down copy of the Sd.Kfz.7 (although later moved onto the smaller Sd.Kfz.10), whilst Breda would produce the copy of the Sd.Kfz.7. However, the two companies had to wait until late 1942 to receive permission from the German company Krauss-Maffei to produce the tracks and suspension of the Sd.Kfz.7.

The Maffei-FIAT 727 (above) and the Sd.Kfz.10 (below). Sources: Compiled by author using Semicingolati, Motoveicoli e Veicoli Speciali del Regio Esercito Italiano 1919-1943 and blueprint.com

Engine and Suspensions

The exact engine model is not known, but it was probably a FIAT license copy of the Maybach HL42 TRKM petrol engine used on the Sd.Kfz.10. The FIAT 727’s 6-cylinder engine produced a maximum of 100 hp at 2,800 rpm. It had a bore and stroke of 90 x 110 mm and an internal volume of 4,170 cm³. This propelled the vehicle to a maximum speed of 53 km/h.

Maffei-FIAT 727 chassis, radiator, and engine during testing. Source: facebook.com

The gearbox was of Italian origin, probably a copy of the German semi-automatic Maybach Variorex-transmission Schaltreglergetriebe 102 128 H, and had 4 forward and one reverse gears with a reducer. The engine was equipped with a Solex carburetor. The tracked suspension consisted of five double road wheels, overlapping and interleaved, mounted on swing arms sprung by torsion bars. The front axle had a leaf spring suspension and shock absorbers. The sprocket wheel had the complicated rollers rather than the more common teeth. This was a complicated system but guaranteed an increased track life. On the rear, the idler wheel was used to tension the track.

Chassis

The Maffei-FIAT 727 had a total weight of 3 tonnes and a payload of 1.5 tonnes. The crew consisted of a commander on the left and a driver on the right. Behind them, there were two rows of benches that could sit 6 soldiers, usually artillery troops that operated the guns towed by the vehicle, which had a tow capacity of 6 tonnes. The windshield could fold forward. A convertible canvas top was mounted at the upper part of the rear body. It fastened to the windshield when erected to protect the crew from the elements.

The FIAT 727 during testing. It was a copy of the Sd.Kfz.10, but with a bodywork similar to the Sd.Kfz.7. Source: wikipedia.org

Like the German Sd.Kfz.10, the FIAT 727 had the engine and transmission on the front, the driving and transport compartment in the center, and a storage compartment on the rear.

The maximum speed was 53 km/h on road in the standard cargo variant. Its range was 240 km on road and 140 km off-road. The average fuel consumption was 45 liters per 100 km on road and 75 liters of fuel per 100 km off-road. The tires were produced by Pirelli of Milan. The rim dimensions were 7.25 x 20”.

Main Armament

The armament of the vehicle would have been the Cannone a Grande Gittata da 75/32 Modello 1937 (English: 75 mm L.32 Long Range Cannon Model 1937). The development of this new gun was proposed by Col. Sergio Berlese. It was a light long-range field gun, but due to the low muzzle velocity, it also had adequate anti-tank characteristics for shaped charge rounds.

Front view of the Cannone a Grande Gittata da 75/32 Modello 1937. Source: comandosupremo.com

The gun’s prototype was produced in 1937 by the Arsenale Regio Esercito di Napoli or AREN (English: Royal Army Arsenal of Naples) and tested later that year. It was designated as Cannone da 75/32 Modello 1937, but not accepted into service.

Between 1937 and 1939, an experimental battery was produced and intensively tested. After a series of modifications concerning the gun’s barrel lenght (decreased by some centimeters) and the muzzle brake, the gun was accepted into service in 1939. A total of 192 guns were ordered in 1940 and produced by the Ansaldo Pozzuoli plant in Pozzuoli, near Naples.

Some senior Italian officers requested the gun should be adopted as the main anti-tank gun of the Italian divisions, but the proposal was denied by the Regio Esercito’s High Command, as it considered it not reliable in that role due to the time the crew needed to put it in battery position and the complex operations to shoot at long distances. The Regio Esercito’s High Command suggested using it as an anti-tank gun only until more reliable guns came into service.

The gun had a weight in battery position of 1,160 kg with the gun shield. Its traverse was 25° to either side, elevation was from -10° to +45°.

There is no information about the trunnion on which the gun would be mounted on the half-track chassis. The decision to mount this field gun is questionable. During that period, the Regio Esercito had in service the Cannone da 75/46 Modello 1934 (English: 75 mm L.46 Cannon Model 1934), developed for the anti-aircraft role but used as an anti-tank gun due its muzzle velocity. It also had a trunnion that could be, with a few modifications, mounted on the chassis of a vehicle. This gun was probably discarded due to its weight, which was about 3,380 kg in battery position.

Cannone a Grande Gittata da 75/32 Modello 1937 fresh out of the factory. Source: Storia dell’Artiglieria

The Regio Esercito probably intended this autocannone to perform the tasks of a support vehicle, and, if necessary, also anti-tank vehicle, leaving the anti-aircraft role to other half-track autocannoni, such as the Autocannone da 40/56 su FIAT 727 and the dual use Autocannone da 90/53 su Breda 61.

In total, only 172 Cannoni da 75/32 Modello 1937 were produced before the 8th September 1943 Armistice. A total of 48 guns were captured intact by the Germans, who renamed the gun 7.5 cm FeldKanone 248(i) (English: 7.5 cm Field Cannon 248 Italian).

Ammunition

During the Second World War, to speed up production, the Regio Esercito used a variety of different rounds that could be fired by different cannons.

Ammunition for the Cannone da 75/32 Modello 1937
Name Type Muzzle velocity (m/s) with first charge Muzzle velocity (m/s) with second charge Weight (kg) penetration in mm of a RHA angled at 90° at penetration in mm of a RHA angled at 60° at
500 m 1,000 m 500 m 1,000 m
Granata Dirompente da 75/32 High-Explosive // 570 (estimated) 6.35 // // // //
Granata Dirompente da 75/32 a d.e. High-Explosive 360 570 6.30 // // // //
Granata Dirompente da 75/27 Modello 1932 High-Explosive 350 490 6.35 // // // //
Granata Perforante da 75/32 Armor Piercing // 630 6.10 70 60 55 47
Granata da 75 Effetto Pronto (early type) HEAT // 580 4.50 55** 55** 50** 50**
Granata da 75 Effetto Pronto (later type) HEAT // 557*** 5.20 * * * *
Granata da 75 Effetto Pronto Speciale (early type) HEAT // * 5.20 * * * *
Granata da 75 Effetto Pronto Speciale Modello 1942 HEAT // 399**** 5.30 * * 70 70
Notes * Data not present
** British estimation
*** Muzzle velocity of the projectile fired from the L.34 gun
**** Muzzle velocity of the projectile fired from the L.27 gun


Three rounds fired from the Cannone a Grande Gittata da 75/32 Modello 1937. From left to right: High Explosive, Armor Piercing, and HEAT. Source: forum.warthunder.com

Crew

As many other autocannoni, the crew would have probably consisted of 6 or 7 soldiers. The vehicle was operated by a crew of 2, a driver on the right and the vehicle/gun’s commander on the left.

The gun crew would have probably consisted of a gunner and 3 or 4 loaders, maybe more. It is not known where the gun crew would have been seated. If the vehicle would have had foldable sides for the rear platform, it could have been equipped with folding seats on the sides. If the vehicle was not to be equipped with foldable sides for the platform, the gun crew would have probably been transported on another vehicle, perhaps an extra FIAT 727 that also transported a decent reserve of ammunition for the cannon.

The Autocannone da 75/32 su Autocarro Semicingolato FIAT 727

The Autocannone da 75/32 su Autocarro Semicingolato FIAT 727 probably maintained the original frame of the Maffei-FIAT 727. This would speed up production, as the chassis for the autocannoni and the standard medium half-tracks would be the same and only later would the vehicles be modified with a gun on a rear platform.

For the same reason, it is logical to suppose that the chassis of the Autocannone da 75/32 su Autocarro Semicingolato FIAT 727 would have the same modifications as those of the Autocannone da 40/56 su Autocarro Semicingolato FIAT 727’s chassis. The frame, engine compartment, and driving compartment would have been identical to the standard Maffei-FIAT 727. The rear platform would have probably had sides that folded 90° to increase the working surface for the gun operators.

Before firing on enemy targets, the crew of an Autocannone da 40/56 su Autocarro Semicingolato FIAT 727 would have had to lower the jacks present on the sides of the vehicle to avoid the risk of overturning and to avoid stress on the suspension. It is probable that this autocannone armed with a larger caliber gun would be equipped with similar jacks. It is unclear if the jacks were manual, as on the Autocannoni da 90/53 su Breda 52 and Lancia 3Ro, or hydraulic, as on the Autocannone da 90/53 su SPA Dovunque 41. The vehicle could probably not have fired without the jacks in place against ground targets because the recoil of the gun would have stressed the vehicle’s suspension.

Conclusion

Very little is known about this interesting autocannone. The only source that mentions it dedicates just a few short sentences to it. Not even the original blueprint survived the war.

The Autocannone da 75/32 su Autocarro Semicingolato FIAT 727 was envisioned on a chassis that was never mass-produced, so it is difficult to hypothesize about its characteristics.

A support vehicle with great mobility would surely have been useful for the Italian divisions which regularly had to rely on improvised armed vehicles during the war.

Autocannone da 75/32 su Autocarro Semicingolato FIAT 727. Illustration made by Godzila.

Autocannone da 75/32 su Autocarro Semicingolato FIAT 727 Specification

Size (L-W-H) 5.55 x 2.00 x ~2.50 m
Weight, battle ready ~ 5 tonnes
Crew 6 or 7 (driver, commander, gunner, 3 or 4 loaders)
Engine FIAT petrol 6-cylinder engine, 100 hp at 2,800 rpm
Speed ~50 km/h
Range 240 km
Armament 1 Cannone da 75/32 Modello 1937
Armor //
Production Paper project

Sources

Andare Contro i Carri Armati, L’Evoluzione della Difesa Controcarro nell’Esercito Italiano dal 1918 al 1945. – Filippo Cappellano and Nicola Pignato – Gaspari Editore – 2008

Gli Autoveicoli da Combattimento dell’Esercito Italiano, Volume Secondo, Tomo II – Nicola Pignato and Filippo Cappellano – Ufficio Storico dello Stato Maggiore dell’Esercito – 2002

Semicingolati, Motoveicoli e Veicoli Speciali del Regio Esercito Italiano 1919-1943 – Giulio Benussi – Intergest Publishing – 1976

2 replies on “Autocannone da 75/32 su Autocarro Semicingolato FIAT 727”

Leave a Reply

Your email address will not be published. Required fields are marked *