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A publicação de qualquer imagem ou informação referentes ao nazismo, fascismo ou quaisquer outros regimes totalitários deve ser entendida como reprodução do rigor histórico e não como apologia a estes regimes, líderes ou símbolos.

M12 Gun Motor Carriage 155mm and M30 ammo carrier - case report

Tankers !!
      This is my new double project: M12 Gun Motor Carriage 155mm and his sister, the M30 Ammo Carrier:
Two sisters with bad attitude...
M12 and M30 walking together...
M12 GMC 155mm ADOLPH'S ASSASSIN - 991st Field Artillery Battalion
in action near Kornelmunster, Germany, November, 1944.
       Although about ten 155mm guns had been mounted on motor carriages in 1918 by Rock Island Arsenal, the  concept of Heavy Self Propelled Guns lay dormant for years, between the Wars. When the WWII began in Europe in 1939, it became clear that the USA would be likely to take part in it, early or late. Therefore, it was decided to develop a self-propelled gun to provide more mobility to field artillery. The choice of the engineers was the old French 155mm gun, from the old inventories of WWI. In June 1941, the Ordnance Committee resumed the works about the concept of a large gun with 155mm in a motor carriage. The 155 mm Gun Motor Carriage M12 was an earliest  U.S. self-propelled gun developed during the Second World War. The pilot vehicle was known as 155mm GMC T6. It mounted a 155 mm gun M1917, M1917A1 or M1918 M1, depending upon availability, a weapon derived from the nearly identical French 155 mm GPF gun. The 155mm guns were virtually identical, and used the same ammunition and propellant. The M1917 was a French gun, the M1918 M1 was American, and when the M1917 was fitted with the breech ring of the M1918 M1, the new weapon was designated as M1917A1.
Philippine Scout soldiers using a M1918M1 for firing practice
      The 155mm gun fired a 44Kg HE projectile to 19.500m. In the M12, the gun was 14° barrel gun transverse easch side and elevation from -3° to +30°. A poor elevation his gun was one of his defects. As the gun was very powerful, the gunners increased the range of the set raising the front of the vehicle with plates, blocks or terrain bumps.
M12s in battery, open fire side by side - Notice that vehicles went into planks
to increase the range of the guns in  indirect fire mode.
      The T6 was built on the chassis of the M3 Lee tank with the engine moved forward to accomodate the mount for the 155mm gun.(some sources claim that later M12s used the M4 Sherman chassis, but this might be a confusion with the M12's use of "Sherman-style" bogie trucks with trailing idlers).  She was completed in February 1942 and shipped to Aberdeen Proving Ground for testings in field.
155mm GMC T6 prototype - father of the M12. Notice the M3 style bogies
and the typical M3 step (filled with bolted armour) in the upper right corner
of the transmission cover ,next to the right headlight.
       The M12 GMC, as the T6, was recommended for standardization on July 25, 1942 and was produced by the Pressed Steel Car Company. An order for 50 vehicles was autorized in July 1942, with the guns themselves coming from Army stocks. This order was upped to 100 vehicles on August, 10, 1942, necessitating the reclaiming the155mm guns that had been used on monuments to WWI.
M12 GMC 155mm - right side view
        The M12 had an armored driver's compartment, but the gun crew were located in an open topped area at the back of the vehicle (04 menbers). An earth spade (similar to a bulldozer blade) at the rear was employed to absorb recoil. This layout: large gun mounted in an open mount at the rear, with a spade was the pattern adopted for many years by other heavy self-propelled artillery.
M12 GMC 155mm standard, with M4 bogies - Notice the rear spade
M12 GMC 155mm - riear view - notice the spade
      During 1943 the vehicles were used for training or put into storage. Before the invasion of France, 74 M12s were upgraded in preparation for combat operations. They were employed successfully throughout the campaign in NW-Europe. Although designed primarily for indirect fire, during assaults on heavy fortifications the M12s were sometimes employed in a direct-fire role.
      The crew manned the gun from the rear, in a similar manner to servicing a ground mounted artillery piece. It was sometime put into service in direct fire support where the formidable gun could easily demolish bunkers and other fortifications. When the 155mm rounds were fitted with concrete piercing fuses they could penetrate up to 6’/180cm of concrete before exploding. It could also make quick work of enemy tanks, though the crew were vulnerable to return fire making this an option of last resort.

M12 resting in the snow. Notice the front locks
      The Artillery Board asked for more M12s, but this was not possible since the supply of M1917 and M1918M1 155mm guns was exhausted. The M12 155mm Gun Motor Carriages were rare beasts, as only 100 of the vehicles were ever built ( and 100 M30s). The fact that they were made available for Operation Cobra shows their importance to Allied Headquarters.  Six battalions were equipped with the M12 and landed in Normandy in the summer of 1944. Because of the speed of the Allied advance across France in July and August 1944, the M12 was often the only heavy artillery support available to the lead armored divisions. When the Army ran into the German Siegfried defensive line they were faced with heavily reinforced bunkers and pillboxes which proved extremely difficult to knock out. Here, the M12 served in a new role as bunker buster, earning it's nickname, "Doorknocker." Thanks to their high muzzle velocity (720m/s) and projectile weight, they proved to be ideal weapon for the direct fire. With special fuzes, the M12's 155mm shells were able to pierce 2 meters of reinforced concrete at ranges up to 1.820m. It was a powerful and well-loved gun by the Soldiers it provided fire support for in combat. 
M12 in direct fire. A very big punch !!!
      Limited storage space meant that only 10 projectiles and propellant charges could be carried on the vehicle. Given this, a similar vehicle, but without the gun, was produced as the Cargo Carrier M30.
M30 Ammo Carrier - left side
M30 Ammo Carrier - right side
      This was designed to transport the gun crew (06) and additional ammunition. In operational conditions the M12 and M30 would serve in pairs. There was a M30 for each M12.
M12 in direct fire action. Notice the M30 parked nearby, to provide ammo.
      The M30, which could carry 40 rounds of 155 mm ammunition, was armed with a .50-caliber Browning M2 machine gun.
M30 ammo carrier 
M30 in urban transit...
M30 in field...A very busy girl...
      The M12 was declared as Limited Standard in May, 1945 and was decalred Obsolete in August the same year. The two surviving specimens are in display at the Aberdeen Proving Grounds, Maryland, and Fort Sill, Oklahoma, USA.


M12 Gun Motor Carriage 155mm

TypeSelf-propelled gun
Place of origin United States
Service history
WarsWorld War II
Production history
Number built100
VariantsCargo Carrier M30
Weight26 tons
Length6.73 m
Width2.67 m
Height2.7 m
Crew6 (Commander, driver + 4 gun crew)

155mm M1917/18 M1 gun
10 rounds
EngineWright (Continental) R975 EC2
340 hp
Suspensionvertical volute spring
220 km
Speed38 km/h (19 km/h off road)
The kits:
      For this project, I 'll use two excellent M12 155mm GMC from Academy (TA 998). Old kits, but very well injected and detailed. The different details of M30 will be made in scratch.
Two kits M12 Academy. Old good stuff...
      There is a conversion kit from Commander Models (#2-006) for this vehicle (thanks, Ian Howes...) , but I want to save on money and squander on the fun ... I'll do the plasticard!! Old School!! Starting by the wheels, as usual...As I already mentioned, the kit is old, but very good. There are parts to you choose spoked wheels or pressed ones, as well as the springs of the bogies being version early and late. So, I decided build the M12 in a late version and the M30 with the early (but not the prototype) suspension version. Let's go:
Cleaning the wheels...I hate this part !!!
Pressed and spoked wheels...
Early bogies for the M30
...and late bogies for the M12
Chassis with suspensions...
M12 : late...
M30: eraly.
       After the suspensions, the interior's building...

       Now, versions begin to differentiate further ... The M30 version had air filters rounded (at least in all the pictures I researched ...) and the floor of the open compartment more recessed (green arrows)
The differences start to become apparent...
The M30's new floor in position (plasticard with 1mm)
The cockpits in weathering. Notice the engine bay in blak...
The cockpits closed. I replaces the  "injected" refrigeration grills by nylon screens ...
The refrigeration  nylon screens ...Much better !!!
Transmission covers in position...
       Scratch time !!!   The M30 under surgery. Plasticard with 1mm and 0,7mm thickness:
Rear compartment under construction...
Lots of fun...

      I'll measure these pieces and make an outline of measures, if anyone wants to take ...
As promised ...

ammo rack

almost there ...
       Some more progress in building of the vehicles
I built the two detachable racks of bags of gunpowder, in the rear.
      For the .50 caliber station, I used this Tamiya's ring and scratch the base with plasticard:
 US 2.5 Ton 6x6 Cargo Truck Accessory Set 1/35 - Tamiya 35231
Browning's Ring...My Precious !!!!
The position of the detachable racks...
       For the M12 does not get jealous, I gave some attention to it, too ....
The Big Gun: 155mm of power !!!


Side by side...
      Well, the building is going...
The elevation rigging for the rear spade in the M12
Another view...
In the M30, the locking pins of the rear door and its chains
Locking pins in position
Adding details...
Spare links in the rear. Field adaptation...
The M12 is almost done...

The two Girls...
       How I used plain plasticard for the M30's rear floor, I ordered a sheet of decals with anti-slip details in Archer. I'm waiting for the decals arrive ...

      The decals arrived, from Archer:
U.S. treadplate pattern ... Hurrah !!
Locations that will be applied ...
Done !!!
No more slipping, now ...
       Aftyer the decals, the colors:
M30 in colors...
Other side...
       And the Girl with big gun (dry-run)

With Future....Next step: decals !!!
      New advances...
M30 Betty Boop decals

M12 Big Boy decals
       Starting the weathering...
M12 Gun Motor Carriage 155mm - left side
M12 Gun Motor Carriage 155mm - right side
M12 Gun Motor Carriage 155mm - rear view
M12 Gun Motor Carriage 155mm - dirty in the chassis
M12 Gun Motor Carriage 155mm - with gun in dry fit...
M30 ammo carrier - left side
M30 ammo carrier - right side
M30 ammo carrier - rear view

      Some more progress .... The completion of this project is close now ....
The vinyl tracks are glued with cyanoacrylate.
"Weight" aspect being placed on the tracks ...
Claws for ammo carrier: .50 with metal kit from RBModel
Notice the details in the vehicle...

M30 - rear view...
Almost done...
The M12 with his big gun in rest position

The two girls, almost ready....
      Well, tankers.... The Girls are ready, finally. First, the Lady with a big gun: M12 Gun Motor Carriage 155mm.
M12 Gun Motor Carriage 155mm - 991 st Field Artillery Battalion
France, 1944.

M12 GMC 155mm - left side

M12 GMC 155mm - right side

M12 Gun Motor Carriage 155mm - 991 st Field Artillery Battalion
France, 1944.

M12 GMC with Kojak and Rover, the dog.
      And the sister of logistics, the M30 ammo carrier:

M30 ammo carrier  - 991 st Field Artillery Battalion
France, 1944.

M30 ammo carrier - left side

M30 ammo carrier - right side

M30 ammo carrier with Kojak and Rover, the dog.
M30 ammo carrier  - 991 st Field Artillery Battalion
France, 1944.
The two girls, togheter!!

      I loved this double project. The M30 version is very easy to do in scratch and the vehicle is very, very beautiful...The Academy kits are old, but awesome...

See you in my next project, Guys !!!  

3 comentários:

  1. Meu caro Serra,

    Pretendo montar um par M12+M30 na 1/72 e estava pesquisando na web. Aí dei de cara com essa página no seu bunker. Montagens fantásticas e instrutivas. Abraços, paulors

    1. Opa... Que bom, Paulors... Nos mantenha atualizado e boa construção!!! Qquer coisa, é só teclar!!!