US/British M3 Medium Tank, "Grant", Part 3

Picture 1:
When Sir Michael Dewar and the other members of the British Tank Mission first arrived in the United States to arrange for procurement of armoured vehicles, their plan was to purchase American built tanks of British design. But it didn't work out that way and in the end the unique British turret was the only major change from the original American M3 medium tank design. It was the Mission's insistence on including the new turret (design by L. E. Carr) that produced the Grant's unique silhouette that we are familiar with today. The new turret was designed to fit the same 54.5in turret ring of the American M3 hull, but the casting was wider to provide more room for the three-man crew inside. It also included a pronounced rear bustle to hold the radio set (originally the No.9 or 11 and then the No.19) which conformed to the British trend at the time of the loader assigned radio operator duty.

To reduce the overall height of the Grant turret the American machine gun cupola was eliminated from the plan and a simple rotating split hatch cover was substituted with a periscope placed in one of the hatches. Except for the split hatch, the other openings in the cast turret included the large gun mantlet at the front, and two protectoscope pistol ports at the left front and right rear. There were also one or two antenna mounts on the back of the roof and an opening to the right of the gun mantlet for the British Mk.1 bomb thrower. In this IWM photo Lieutenant-General Bernard Montgomery, GOC 8th Army, stands in front of a Grant he might have used as a command tank for a short time in 1942. Notice his black RTR beret with both the regimental badge (silver) and his general's cap badge (yellow and red). Also notice the interesting double "I" rubber block track (WE210) used on these particular vehicles. Although this Grant has the later canvas dust cover protecting the 75mm gun's mantlet, the gun remains the short M2 model and there are no stabilizers on the main weapon. Some command tanks sported dummy 75 and 37mm guns, which provided more room inside for radios and map boards. A sun compass and what I suspect is a mount for an anti-aircraft .30cal Browning machine gun are up on the turret roof.

Picture 2:
Another picture from the same promotional series with Montgomery shows a bit of the turret roof detail. Here we see the opened doors of the split hatch with a bit of the periscope visible in the open half to our far right. To Montgomery's right is a sun compass, a common addition to many British AFVs used in the North African campaigns. The sun compass was a simple instrument that determined general compass direction by the use of the sun's shadow falling on a round dial, requiring the operator to also know the precise time. I believe the curious tall bracket with rod handle you see welded onto the hatch ring (to the General's right) is seen only on rare occasions on Grants and is a support for a Browning MG, although some sources suggest it is a bracket for a spotting scope Montgomery is said to have used. Notice the screws that hold the 37mm gun mantlet to the turret and the use of pennants on the radio antenna behind the split hatch for identification. The large split hatch was the only hatch opening on the roof, so in an emergency one or two of the other turret members had to find another way out of the tank, typically via the turret basket access openings and then through the hull side doors. Recall that the split hatch could fully rotate and allowed the commander a full 360 degree view when using the Mk.1 periscope. Originally, the turret was drilled for only one antenna, but when the No.19 radio was fitted a second was necessary. In many photographs this second base was attached to a welded bracket at the back edge of the turret.

Picture 3:
If we drop down through the split hatch into a typical Grant 1 we will see this general view of the equipment at the front of the turret. The main gun up here is the US 37mm Gun M6 in the M24 mount although during shortages the earlier M5 gun was also installed. The major differences between the M5 and M6 weapons were the earlier M5's six inch shorter barrel and the fact that it had a manually operated breech. The M6 with a semi-automatic breech was capable of firing 30 or so rounds per minute and could be elevated manually from +60 to -7 degrees in this mount. The turret was either manually or power rotated, the power produced from a hydraulic system similar to other US traverse mechanisms of the time. With the power traverse operating, the turret could be fully rotated in around 20 seconds.

This cleaned stowage sketch from the Users Handbook shows the gunner's seat bottom at the lower left without its tall back and cushions. Directly forward of the seat are the gunner's laying controls, including the manual traverse handle hanging down with its brake palm switch clearly shown in the center of the mass of machinery and pipes. The manual traverse housing contains a brake to keep the turret stationary when the vehicle is on a slope. By pressing the palm switch, the gunner could release the brake before the turret was rotated. Although it is difficult to see here, the black hand grip for the power traverse is to the right of the manual control, but we will have a closer look in a moment. The elevation hand wheel is attached to the left of the gun mount and cannot be clearly seen here, but the reservoir container for hydraulic fluid for the power traverse is mounted on the turret basket wall under the laying equipment.

Above the gun laying controls is the mount for the gunner's periscope sight, in this case it was the M2 periscope which fit into the mounting box so the face pad you see would surround the viewing glass to protect the gunners face while sighting. A signal pistol is seen in its holster at the upper left and a 2in mortar bomb thrower Mk.1 is seen fixed in the turret at the upper right. For some reason the British either removed the bomb thrower from many of their tanks in Africa or it was never installed in the first place--many photos show the resulting hole plated over. The coaxial machine gun for the 37mm weapon is another .30cal M1919A4 Browning, this one mounted to the right of the 37. Because the ammo feed for the coax is on the left side of the receiver, the ammo box support was mounted on the left of the 37mm gun and an ammo chute directed belted rounds over the gun tube and then down into the Browning. To the right of the MG is a bracket for its oil can and cleaning brush, and right next to those items is a Silverlite hand flashlight.

The longer bin to the right contained 14 smoke bombs for the 2in Mk.1, and the thin box to its right held two additional protectoscope prisms for the opening flaps at the right rear and forward left of the turret (not shown here). Next to the racks for 37mm ammo you might make out a signals satchel bag (containing the loader's radio headset) which is next to a portable fire extinguisher. Also in the same area is the vertical support with oblong holes that held the loader's seat when it was not dropped out of the way during battle. The holes allowed the seat to be adjusted in height by sliding it up or down the support and then pinning it in place. According to the original stowage sketch, the larger bin closest to us held six 100 round .30cal ammo belts.

Picture 4:
Here is a closer view of the gunner's manual and power traverse equipment. The manual crank handle hangs in the middle of the illustration with its palm switch brake control clearly seen. The gunner used his left hand for this crank, so the palm switch would naturally fall into his palm as he closed his fingers around the crank handle. Just to the left of this handle is a long lever that is the manual turret traverse gearshift and clutch, allowing two speed manual traverse. At the bottom of the picture is the hydraulic fluid reservoir with its filling cap on top, and above it is the electrical junction and control box for the power traverse. An electric motor on the turret floor pressurized the fluid that would then feed the hydraulic motor you see attached to the turret lip. A slightly larger electric motor and pump was required to supply both the power traverse and the gun stabilizer, when it was installed (not shown here).

The power traverse grip handle is now a bit clearer at the right. The hand grip could be rotated to the left or right to traverse the turret in either direction. The amount of twist determined the speed of the traverse. Notice the two hydraulic hoses from the power traverse control unit that attach to the hydraulic motor housing. When the hand grip was rotated to one side it opened a valve allowing pressurized hydraulic fluid to flow through one of the hoses to one side of the motor propeller. The amount of twist determined the amount of flow of fluid and therefore the speed of the traverse. Twisting the handle the other way allowed fluid to flow to a valve on the other side of the motor, rotating the motor fans the opposite direction and therefore rotating the turret that direction. As you can see the hydraulic motor is attached directly to the turret lip and a hidden gear in the case engages the gear teeth surrounding the turret ring under the lip.

Picture 5:
Here is the cleaned official stowage diagram of the rear of the Grant turret, showing more storage for 37mm rounds and the large radio up in its bustle rack. The first radios used in Grants were either No.9 or No.11 sets that required only one antenna. But later, around the time of the Alamein battles, the No.19 set became available and quickly replaced the other two. These newer sets required two turret antennas, one much shorter than the other, attached to entirely different antenna mounts. Counting radio antennas on the turret of Grants is one technique you can use to approximately date Grant photos, assuming the transition from the No.9/11 sets to the No.19 was fairly rapid). The radio drawn here is a No.19 W/T set, but most of the connecting cables have not been drawn. Down below at the left is the red portable fire extinguisher we saw earlier and above it is a flag set used for recognition between other AFVs and support troops. To the right of the vertical 37mm ammo racks is another flag set, this one comprising three distinguishing flags as well as three yellow pennants. The commander's seat is identical to the loader's and is mounted on a similar vertical bracket so the seat can be easily adjusted in height.

Directly above the seat on the turret lip is a cluster of stowage bins containing spare periscopes and protectoscopes as well as six hand grenades (the box on the bottom left). Also in this area is a bin for the commander's binoculars, a large Hellesen lamp and smaller Silverlite lamp, and the radio connect box that both the commander and gunner's head sets plugged into. We saw the loader's radio connect box (the loader/operator's is a No.2 and the commander and gunner both use No.1 boxes) earlier on the other side of the turret. Up on the ceiling is a padded shelf for map storage and to the left of the radio is the cylindrical variometer for the aerial base No.8 (mounted just above it). The storage box to the left of the radio is for spare radio tubes (valves) as well as other radio parts and you can also see the edge of the right side protectoscope/pistol port at the far left of the drawing.

Picture 6:
This photo taken from the driver's seat looking up into the turret was taken in one of the Grants preserved at the Tank Museum at Bovington. The gunner's black seat back and bottom cushions are installed and the commander's small round seat is also visible behind the gunner's. Both seats had wide US style seat belts but just the commander's are visible here hanging down from the back. The M3 turret basket was enclosed in sheet metal to protect the occupants while traversing, but there were two access openings. This is one of them, obviously just forward of the gunner's position, which allowed him to escape the basket and tank through the left hull door (just out of view here). This opening also allowed the driver or 75mm loader to pass 37mm rounds into the turret from the stowage bin on the vehicle's left sponson. The other turret basket opening is on the left side and also allowed quick escapes from the vehicle via the hull side doors and the passing of ammo and other material from one space to the other. Also visible here are a couple of the typical British water bottles siting in their non-rotating bin at the front of the basket wall.

Picture 7:
This is a similar view of the inside of the Grant (II?) we saw earlier that was at Bassingbourne Barracks but now resides at the IWM. In this case we are looking up at the right side of the basket and turret with the forward access opening to our far left. The vertical support to the right, next to the empty 37mm ammo racks, is the support for the loader's seat, the bottom of which is barely visible at the bottom of the image. Directly above the seat is the bin for 2in smoke bombs (minus its front panel) and to its right is the flat bin for two extra protectoscope glass blocks. The loader's radio connect box is directly above. Notice the characteristic British radio wire and plug ("drop lead") hanging from the box. The plug was called a "snatch plug and socket" and was designed to pull apart easily when the owner of the headset decided to bail out of the tank without first disconnecting. Next to the smoke bomb bin on the left is the Mk.2 bomb thrower, shown here hinged open and ready for loading. The bomb thrower was mounting was non-rotating requiring the turret to be rotated to aim the weapon. Interestingly, this particular vehicle is also equipped with the more primitive communications system of funnels and tubes, in this case I have been told there were three of these stations in this vehicle, one for each of the crew members. Perhaps this tank commander just didn't trust the new fangled radio sets for communication?

Picture 8:
This photo taken by Jim Hensley of the Grant owned by Alan Cors of the Virginia Military Vehicle Museum provides another excellent view up into the turret from the turret basket front access. This time we can see further up at the underside of the 37mm gun and beyond to the split hatch in the roof. Again the commander's small round seat is visible with some of the equipment bins behind it. This radio is a No.19 set and the small box below the radio shelf held spare radio parts and tools. One of the improvements incorporated into the No.19 W/T set when it was built was a combination of both external and internal two-way communications equipment combined into one box. The No.19 was also lighter in weight and smaller in size than the older radios and required less current to operate. The basic set is composed of two primary boxes, the smaller power unit on the left in this mounting and the larger transceiver on the right. Normally there was a protective cage around the front of the unit as we see here to keep casual body bumps from changing settings. Most of these radios in British tanks had a light gray face panel, but those manufactured in the US and Canada could be black or green.

Picture 9:
This is a TM photo of the 37mm gun M6 in the M24 mount. The main components are easily identified and include the elevation hand wheel at the bottom, the gun barrel and breech, and the long recoil guard at the rear. There was typically a olive drab green or khaki canvas collection bag below the recoil guard to catch spent 37mm brass shells as they bounced off the inclined surface at the back of the shield. The 37mm gun was a popular gun in the US military in the late '30s and early in WWII. It was lightweight, powerful for its size, and could fire a number of different ammo types specially designed for it, including solid AP shot and HE rounds. This M6 model in the Grant is very similar to those found in other US AFVs such as the M3/M5 Stuart tanks. But you can easily identify this M6 (with its semi-automatic breech block) because the large breech opening spring/cylinder can be can seen on this side of the breech, partially hidden behind the gunner's shoulder shield. The rotor shield on the left is the mount for the gunner's periscopic sight M2, the periscope not mounted here but the large protective face pad is. The 37mm weapon used a percussion primer striker but was normally electrically fired by a solenoid you see below the gun mount, just before the breech ring. As with the 75mm gun, there was an emergency back up firing button that mechanically fired the gun.

Projectiles available to Grant crews included the US APC M51 (APCBC-T), AP M74 Shot (AP-T), HE M63 (Shell), plus an M2 canister round with 122 steel balls packed inside. The maximum range for the APC M51 shot was around 12,000 yards but typical combat ranges with the sights then available were typically less than 1,000 yards. The same M51 APC could defeat a little less than 2in (50mm) of face hardened armour at 30 degrees obliquity at 1000yds, but this performance was considered inadequate for anti-armour work by the time of the Gazala/Knight's Bridge battles of 1942.

Picture 10:
This is the last image in Part 3 of our exploration of the US built and British operated M3 Grant Medium Tank. Perhaps because it was only meant to be a stop gap design while a medium tank replacement could be developed with a 75mm gun in a rotating turret, the M3 turned out to be one of the more interesting, if limited, tank designs of WWII. As far as the British were concerned when they were facing the German and Italians in Libya/Egypt, the Grant was a vehicle desperately needed. Along with the M3 Stuart also used by the British, the Grant helped set the standard for firepower and reliability, something sorely missing up to that point on the British side of the wire in North Africa. American Army instructors are introducing these RTR troopers to their new Grants in this Imperial War Museum photo. Notice that the insides of the hull doors are painted olive drab in this batch of Grants. By the way, a few American M3 Grant tankers under British command recorded the first German tanks destroyed by US forces. The troops had been sent to North Africa for training and after their experiences in North Africa they returned to the US to pass their knowledge on to other tankers.

I would like to thank Jim Hensley for loaning us his interior photographs of the preserved Grant tank located in the Alan Cors collection at the Virginia Military Vehicle Museum. Jim has been kind to AFV INTERIORS in the past and his contributions to the Web Magazine are always greatly appreciated. Jim is also the web master for the Washington Armor Club web site which is packed with excellent articles and other armor reference information. I would also like to thank the always energetic staff of the Patton Museum of Cavalry and Armor at Ft. Knox, Kentucky.




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