GMC 353 Bofors (1943)
USA/France (1943). c19 converted
A potent Allied SPAAG
The story of allied SPAAG (Self Propelled Anti-Aircraft Gun(s)) is one of lesser commitment to organic defence of its assets, since an air supremacy inbalance in favor of the latter was soon gained. This capabilities was seen as an afterthought by belligerents in 1940-41, but after the US entry into the war, the ramid ramping up of the British air power, then US from November 1942, marked the end, of axis air balance over Africa. Onthe eastern front by mid-1943 already Soviet air force took the head and gradually gained supermacy. In Europe after June 1944, allied air supremacy was definitively gained anf organic AA defence for the Wehrmacht became a priority. Tanks were of course prised based for SPAAGs such as the FlakPanzer I, 38(t), III, IV, Möbelwagen, Wirbelwind, Ostwind or the experimental Kugelblitz, but trucks were also cinverted for the purposes starting in Africa by 1942 already, in "portee": The AA gun was carried on the flatbed.
The T68 prototype
On the allied side, organic AA protection for armoured regiments was started by the British early on, which developed a specialist tank SPAAG, the Crusader AA Mk I-II-III, but they failed to do some impression, too slow in traverse. The US soon devised various SPAA based on its half-tracks in order to give them a better all-around mobility than trucks and support regiments. The M2 for example led to the T28E1 (1942) with a single 37 mm AA, tested with success in Africa. The M2 for a start had up to three MG with AA mounts, a cal.50 and two cal.0.3 on pintles with elevation. Before even that was developed the 1941 T1, later T1E3 with its Bendix turret (from a B-25 Mitchel bomber) and two .50 cal. machine guns, but it went nowhere. However more trials led to the adoption of the Maxton mount. In 1942 base don the M3 came the M13 SPAA and later the T16 SPAA with the M45 “Meat Chopper” quad .50 caliber turret which became the prime allied SPAA until the end of the war. However few attempts had been made on regular trucks due to the availability of the better Half-Tracks.
About the GMC truck
The
GMC 353 was the most common US tactical truck of WW2, with more than 570,000 made until 1945 at Detroit. Wether it was called "Jimmy", "Deuce and a Half" this bedrock of the red ball express in late 1944 allowed the allies to push forwards towards Germany and stayed supplied. Given ordnance rules and strict separations, these trucks were rarely declined into portee vehicles for any kind of ordnance. They were only used for supply and transport, sometimes defended by their own ring-mounted cal.50 M1920 HMG.
Highly modular, the vehicle came as the open or closed cab, long (LWB) variant as CCKW-353 or short (SWB) variant as CCKW-352. The CCKW coupeld a strong 6x6 chassis with the GMC 270 engine. This was an overhead valve, inline six cyclinder, rated for 91.5 hp (68.2 kW), and later 104 hp (78 kW) at 2750rpm with 216 pound-feet (293 Nm) of torque at 1400rpm. It ran on gasoline but ran of civilian grade as well as of oil. Very reliable, this power unit was was coupled with a Warner T93 5-speed transmission. Its manual gearbox counted a 4th gear and overdrive on ot 5th gear. The transfer case had high and low gears engaging the front axle, and these axles were of the Timken split type and later the GM "banjo" type.
The CCKW 353 had a long or 164 in (417 cm) wheelbase. It had eight roadwheels with 7.50-20 tires, paired on rear axles, singles forward. The driver had hydraulic brakes using vacuum. The were blackout driving lights, army towing hook, and foldable banks for the troop carrier. Some vehicles had a 10,000 lb (4,500 kg) front-mounted winch capable of 300 pounds (140 kg) of traction, and 14 inches (36 cm) wide.
Enters the Free French
Many of the former trucks delivered by lend-lease to the British Army were also sent to other allies, such as the Free French Forces, reconstituted as a 1st army under Gral De Lattre fighting in Italy, and thrown into action in Operation Anvil Dragoon in France by August 1944. The French wre US-supplied and thus, had to conform to US armies organisation, to the dismay of De Gaulle which did not wanted to "waste" men in non-fighting roles. Anyway, the French had their own organic supply train for their armoured brigade and notably the famous 2nd DB or second Division commanded by the brash and impatient Philippe Leclerc de Hautecloque.
The French in Italy were delivered seventy M16 Multiple Gun Motor Carriage (MGMC), and purchased many more on the stocks after the end of the war, to reach a total of perhaps 800, and still around 300 as late as 1983. It was well appreciated for its dense firepower, thanks to four cal.05 Browning HMGs with the fast M45 mount. It was just deadly for low-flying aircraft. However against higher altitude aircraft, it clearly lacked the reach and punch to destroy their targets. As the previous SPAA were removed from service or reconverted, there were surplus earlier Maxson Mounts and some crafty workshoppers managed to create with available GMC-353 trucks an impromptu conversion in portee. This field variant was never standardized, but many were made, and later others were converted with the M45 Quadmount, especially if their platform was destroyed. Their greatest users were the French, again, which were more lenient about these conversions, and The French Army postwar used M45s based on trucks to deal with ambushes, a distant relative of Vietnam gun trucks. Four were present during the Battle of Dien Bien Phu.
However none so far through of bringing a heavier naval AA ordnance on these vehicles. The use of the 20 mm Oerlikon or the 40 mm Bofors were tested by the US but rejected due to weight and space issues. Only the British managed to create a twin Polsten gun arrangement (lighter and smaller than the Oerlikons) on their half-tracks. The quad 0.5 in cal. in drum-like rotating mount -T37) was not adopted in 1941, neither the T10 with twin Oerlikon, which nearly entered service until cancelled due to the lack of 20 mm guns, already accaparated by the Navy. But the most outstanding and freaky conversion wads the twin tandem 40 mm Bofors T68 Multiple Gun Motor Carriage. Too heavy, unwieldy and unstable, it was cancelled in June 1943 as well as a single Bofors T54 and T54E1, and Elco Quad 20 mm M2.
The GMC 353 Bofors design
This conversion was done, giving some sources (see below) as early as September 1943. According to the photos, the French took the late open cab variant, which freed space notably forward to maximize the arc of fire of the gun, especially when folding the front windshield
Like here. This allowed the gun to be depressed down to 90°, facing forward so it could be used in ground support, one of the missions of the vehicles, as the Luftwaffe in France by late 1944 was no longer really a threat.
The flatbed was kept but its metallic walls removed as well as the former back door. Instead, a bunk was built at the rear, for the gun crew to seat (3-4) containing also the ammunitions. More ammo crates were stored nearby or fitted under the chassis, forward and rear, everywhere possible. Forward of the flatbed there was a bin containing the gun's maintenance kit and toolbox. Four jerrycans were also carried, suspended under the forward chassis close to the spare wheels, placed on either side of the open cab.
On this flatbed was installed the full mount of a usually towed, quad wheel chassis Mark I or II Bofors L/60. The conversion was definitive as no photos shows the removed wheels or other parts of the chassis. This installation, free from interferences by leaving the flatbed flush-clean lacked however any form of protection to day the least. In case of a bad encounter, the whole crew was easy meat. This was perhaps one reason why this installation was never adopted in US practice.
But this was more than compensated by the awesome firepower brought by the Bofors Bofors 40 mm/60 (1.57") Model 1936 (Mark I). Weighting 1,150 lbs. (522 kg), 148.8 in (3.780 m) long, it was capable of 120 rounds per minute cyclic per barrel nominal, 80 in practical conditions, and was able to fire the HE Mark 1 Mods 1 to 24 - 1.985 lbs. (0.900 kg) round or even the AP M81A1 and M81A2 - 1.960 lbs. (0.889 kg) in ground support when available at 2,890 fps (881 mps) muzzle velocity. Barrel life was circa 9,500 Rounds. It could reach any target at 11,019 yards (10,076 m) at 42° elevation. Armour penetration was impressive as well, up to 2.70 inches point blank (69 mm), up to 1.2 inches or 30 mm at 2,000 yards (1,829 m) and 0.6 in or 15 mm at 4,000 yards (3,658 m). Only limitation was the stamina of the loaders, manipulating these heavy five-round cartridge (gravity feed) and skills of the operators and pointers, five men in all.
The GMC 353 Bofors development and in action
The origins of such conversions started withing the 22th FTA, which included a battery command and 4 gun batteries, all towed Bofors. The command battery comprised a command, communications, supply, repair, material and health sections. Each battery consisted of two four towed guns and their prime movers, and a recce unit. The first photos of these vehicles were taken in the 22th Colonial Group of Anti-Aircraft Land Forces and by 16 September 1943, the 3rd colonial artillery battery light DCA ("Defence Contre Avions") became organic of the famous 2nd Free French Division originally created in Chad, Africa, and was designed to protect the Leclerc column, under Captain Lecole. It was deployed 14 km south of Rabat and formed the basis for the 22nd Colonial AA Group.
In October-November the unit was under command of Captain Lancrenon which moved its unit to Camp Cazes in Casablanca, to defend the raiklways and depots against any incursion of Kesselring's remaining Luftwaffe assets from Sicily. The unit was reinforved by Jeeps, Dodge and Ford 3 t trucks and CMP trucks towed extra 40 mm Bofors Mk1 and Mk2 Bofors.
17-19 November saw training with the 25th AA colonial Group, shooting at a fabric sleeve target towed by a Leo 45. Studies were made at a local workshop on adapting these Bofors to the long chassis CCKW 353 and by November 24, a single vehicle was used as prototype, registered 415920, and was modified in the local workshop, making the conversion. It was tested by December 1943 at the Aïn Diab range, 60 shots fired in two configurations, wheels braked or with stabilizing feet. More trials were done at the Mediouna firing range, 64 shots.
After 154 fired, the prototype was fully examined, dismantled to study parts fatigue and cracks. It seems the chassis withstood these tests without a hitch so by December 2, Squadron Leader Lancrenon and Lieutenant Massiah presented the GMC autocannon to Major Luchenbach, the US adviser of the division for an authorization of conversion, by default of a standardization. Later, it was examined by officers of the Us Ordnance Corps, witnessing more fire tests in Algiers at Hussein Dey and eventually Guystville in front of French-US staff. By January 12, 1944, General Leyer have approval to have 16 Bofors converted into SPAA using the GMC 353 chassis. Work started the 17th at the EPSM of Casablanca and by mid-April 1944, 14 were in service. Eight were provided to the 1st battery, six in the second.
On April 26, an effort to made extra conversions for the 3th and 4th battery started at the EPSM in Oran and in May 4, the last were delivered, with the whole batteries sent to depots in Great Britain. Leclerc's 2nd DB indeed was ordered there, leaving Africa for the expected D-Day. In Britain, the 22nd AA Group trained until June 1944, but the French took no part in D-Day and only by 31st of July, the Division crossed the channel to Normandy at Utah Beach and assets were gradually landed in early August. By that time the breakout in Normandy with Operation, Cobra was done, and the allies moved steadily eastwards.
The group was deployed to defend the Division's routes, parking areas and ended in Alençon, east Normandy, and by August 12, the second battery was ambushed at Colombier by German infantry, whole the 4th battery (Radon group) also met opposition, having one dead, one missing. Soon the lack of armpur led to the creation of battery protection units organic to SPAA batteries, called "free groups". On August 13, 1st Battery downed its first German bomber over Alencon. Next was the march on Paris, the batteries still dispersed in road protection and by August 24, the 3rd battery in Jouy-en Josas met heavy opposition, with three vehicles destroyed, urging the rear workship to convert three new vehicles in replacement at Vincennes near Paris.
On August 27 the 1st battery entered Paris and was stationed at St. Mandre in the east, soon encountering German semi-tracked vehicles taking refuge in a building. From then on, they would bring fire support, often guided by resistants, in urban combat against fleeing or entrenched German infantry. The HE shells did wonders on walls and any obstacles. Later the 1st Battery protected bridges of Austerlitz, Nation and Bastille. The 4th battery was sent to Place de la Concorde and saluted General De Gaulle during its triumphal march and parade. On September 8, the 2nd DB left Paris and on the 13th, the 4th Battery was at Dompaire where, later capturing 30 prisoners while the 2nd while protecting a bridge at Nomexy-Châtel (Mosel) and Meurthe at Menil-Flin was taken under German artillery fire. Late the 2nd bat. was sent to Azerailles.
The French in October-November 1944 however in their push to Alsace and the German border were desperate for more firepower. Despite of this, the pace of the push meant there was no time for more vehicle, even though Vincennes workshops could provide more. Needless to say there never was a CKW 353 2-1/2 tons Bofors standard. The longwheel base variant chosen made sense for its larger space and availability, with that not many or complex modifications made in order to accomodate the gun and its platform. It is unclear however how many conversionse were made with a more likely total of 16, four per battery, four batteries with the 2nd DB. Apparently given the available photos, most photos were from late 1944 and early 1945.
Surviving vehicle of the 2nd DB today (pinterest).
The final chapter of Leclerc's Bofors GMCs was when the advance resumed at the end of October, pushing to Baccarat and the last day of the month, the 2nd Battery shot down a FW 190 and soon after six Me Bf 109. On November 23, the 22nd AA Group entered Strasbourg and took positions in several places. After a while some batteries were detached and dispersed for cover fire and clean-up operations. On 31 December 1944, they were replaced in the 2nd DB by newly formed units using the M16 MGMC and they were reassigned to the 15th American corps in the Saarland and ater to reduce the Colmar pocket, without air activity they still shoot down some aircraft at Obersaasheim and Neuf-Brisach. By March 1945, the Group claimed 17 enemy aircraft destroyed, 6 damaged but also captured in ground operations some 800 prisoners and a lot of material. It went on uktil the end of the war in France and was eventually disbanded by March 31, 1946. The French will go back to the formula, in Indochina, and even allegedly devised an armoured variant, but this is to be futher explored.
Read More/src
VMI, N°6 du 19 june -15 aug 1985 and VMI, N°9 15 december 1985.
'La 2e DB en France, Combats et Combattants'. Edition: Arts et Métiers Graphiques. 1945
Le GMC Bofors ou L'Autocanon de 40mm sur GMC
ww2 pics, Autocannon GMC CCKW 353 BOFOR 40 mm
cckw.org
Armoured variant in Indochina
leicestermodellers.weebly.com
old-forum.warthunder.com GMC 353 maxton
tankhistoria.com, US SPAA
forum.warthunder.com/
model on panzerserra.blogspot.com
decals