Sherman 75mm turrets

The initial design of the Sherman 75mm turret can be seen on the T6 pilot above. This turret featured a gunner's rotor sight device (1), pistol ports with M3 Lee style protectoscopes (2) on both the left and right sides, the M3 Lee machine gun cupola (3), and a very simple gun shield (4) without any sort of protection for the gun's rotor (5). Note that the turret and the gun shield were not equipped with lifting rings.

The challenge in the development of the US Medium Tank was to design a superstructure that could carry a turret large enough to accommodate three men and mount a 75mm gun. For this purpose, it was thought that the turret ring would need to have an inside diameter of 69 inches. In retrospect, this was one thing the designers "got right" from the start. It was determined that the turret of the new Medium Tank would be cast armor, while the upper hull would be of either welded or cast armor construction. Above shows a left rear view of the T6 turret. On subsequent turrets, the M3 type protectoscope (1) was replaced with a solid door, and the pistol port on the right side was eliminated from the design altogether. Originally, the T6 turret did not have lifting rings (2). These were added to the turret and gun shield during development and became standard. The 30 October 1941 date of the photo gives an idea of the chronology. Another item that was retrofitted to the T6 turret is the secondary antenna bracket (3) which also became a standard feature. The turret basket was encased in steel mesh (4). It wasn't until early 1943 that the Ordnance Department acknowledged that this was a safety issue, since the mesh "trapped" the turret crew, and isolated the drivers. In April, work was begun to redesign ("skeletonize") the turret basket. In August 1943, as part of a more comprehensive "Quick Fix" Modification, the mesh was instructed to be removed from existing Shermans.

T6 turret

In this view through the commander's hatch opening, note the brackets (1) installed in the turret bustle. They could accommodate either the US or British standard tank radio. The commander's (2) and loader's seat (3) were affixed to the turret basket wall and were height adjustable. A bit of the 75mm gun's breach and breach guard (4) can be seen. With only one hatch in the turret, the breach guard presented an obstacle to the loader as he attempted to escape in emergency situations. During the initial design work, a loader's hatch was considered, but rejected in the interest of simplicity. As a result of numerous combat reports, a loader's hatch was added as a standard item on Sherman turrets in late 1943. Twelve ready rounds can be seen mounted to the wall of the turret basket. Ready rounds were very popular with tank crews but were extremely vulnerable. Along with the steel mesh around the turret basket, the "Quick Fix" Modification ordered the elimination of the ready rounds. Not only were they vulnerable, but as is evident here, when in place, they also blocked the crew's escape.

"Low Bustle" D50878 75mm Turrets

Early low bustle with rotor sight device

The Sherman design was still being revised as the first tanks rolled off the assembly lines. Some early M4A1(75)s can be seen to have rotor sights as on the T6 pilot turret. The exact number is unknown, but a Lima memo dated 21 January 1942 provides a clue when it states, "First 30 tanks using Rotor Device." It is thought that 10 or so of the early Pressed Steel Car M4A1s also had rotor sight turrets. The rotor sight was vulnerable to being fouled by bullet splash and by April 1942, a revised D50878 casting that incorporated a gunner's periscope replaced it in production. As best we can tell, no other company's Shermans used the rotor sight device, so this should only be seen on very early Lima and PSC M4A1s. The rotor sight device was considered "not-battle worthy", and such turrets were not to be shipped overseas to combat units. However, at least one slipped through the cracks - a period photograph (right side) shows a "rotor sight" M4A1 on a Sherman of the 751st Tank Battalion near Montemarano, Italy on September 29, 1943.The left side photos above provide front and rear views of the rotor sight casting on the only surviving Sherman known to have this feature. This is "Michael", the second M4A1 produced by Lima Locomotive Works. It would have been accepted in March 1942 and is the earliest surviving Sherman in the world. It is on display at the Tank Museum at Bovington in the UK.

The rather simple gun shield used on the T6 pilot was replaced with a heavier casting (1), Part Number D50880 as seen here on "Michael" at Bovington. A rotor shield (2) was added to protect the gun works from bullet splash. This combination of gun, gun shield and "narrow" rotor shield was labeled "M34 Gun Mount." The gun shield was equipped with lifting rings (3) and on some early production Shermans, they were welded on very close to the rotor shield as seen here. Some of these "close mounted" lifting rings got damaged and bent inward in service, which caused them to foul against the rotor shield, and disable the elevation of the gun. Consequently, in the Summer of 1942, the lifting rings were ordered to be mounted further away from the rotor shield.

The original design of the T6 pilot included the odd machine gun cupola as used on the M3 Lee. However, in a conference on "presentation day," 3 September 1941, it was determined to replace it with a commander's split hatch cupola similar to the one the British had designed for the turrets of their M3 Grants. The photo above shows the hatch on "Michael." It can be seen that both the hatch ring (1) and the hatch halves (2) were castings, and we would point out to plastic model companies that the hatch halves included "ridges" (3) on their outer edges. On this example, the anti-aircraft machine gun pintle (4) that was part of the hatch ring casting is small and includes some sort of tightening fixture bolted on (inset). We suspect that the use of this "small pintle" casting was limited like the rotor sight, to some of the first few M4A1s produced by Lima and Pressed Steel Car. If one assumes that the factory orientation of the pintle was facing front, then it can be said that the revolving periscope (5) was mounted in the right-side hatch "flap" as the British called it. For some reason, the British did not include a lifting handle on their Grant cupolas, and the omission of this simple component appears to have carried over to the Sherman series for the first several months of production. Just looking at the photo above, one wonders how users were supposed to lift the hatches.

As mentioned, the T6's turret had pistol ports with M3 Lee style protectoscopes on both the left and right sides. Production D50878 turrets had a pistol port on the left side only, and the solid door casting was somewhat larger than the protectoscope. On "Michael," the door's part number can be seen as D 51289 with the "S in a circle" logo indicating the piece was cast by Symington-Gould of Rochester, New York. The same logo is seen on the armored gas cap covers (1). Indeed, the "S in a circle" logo appears on many of the cast components of "Michael" including the drivers' hatches and direct vision blocks. The fire extinguisher pull housing (2) is mounted in a non-standard position facing up. The standard position was facing to the rear.

The montage above shows the pistol port in the open and closed positions from both inside and outside the turret. One of the authors recently had the opportunity to operate a pistol port, and his first impression was that it was much heavier than expected. The L shaped handle or “lever,” served as a simple prop, which held the door open, and locked it into position by means of a “lever locking pin” (1) which could be slipped into a “notch” (2) with a rotation of the handle. To secure the pistol port door in the closed position, the handle was rotated until a fixed “latch” (3) contacted a fitting (4) welded on just above the pistol port opening. The “lever handle” (5) was installed with a rubber bicycle type grip which is missing from this example.

Based on feedback from the using arms, a number of changes were introduced into production in early 1943. A direct sight telescope was added, & to protect it & the coaxial MG, the rotor shield was widened. The new configuration was labeled "M34A1 Gun Mount".

The first version of the M34A1 gunshield had lifting rings & attachment flanges on the top, bottom & right side (left-side photo). The final version of the gunshield eliminated the lifting rings, & moved the right side attachment points to the inside of the turret, thus dispensing with the outer flange on that side.

Split hatches

There were a number of reports of crew injuries because the locks of the original design of all of the Sherman's hatches were insufficient. When in the open position, the heavy hatches were liable to slam down when they brushed against tree branches or when the tank bounced around violently as tanks do. As a result, positive hatch lock mechanisms were introduced into production (circled in red) beginning around the Spring of 1943, and modification kits for all of the hatches were provided for depot and field retrofit.

A spot light (circled in red on the center picture) was also introduced in early 1943. Many of the earlier turrets that lacked the spot light & its fittings (left-side photo), had them retrofitted during later upgrades. The right-side photo shows how the spotlight was mounted on the fitting.

Turret thin spot

Two sections of the right front interior of the turret were thinned or scooped out to prevent "the knuckles of the operator from being skinned or barked when using the hand traversing mechanism." As the Sherman entered combat, reports came in that the enemy aimed for these "thin spots." To protect this area, a patch on the right front of the turret was introduced around Spring 1943, and modification kits were provided for depot and field installation. The photo on the left shows the thin spots on the interior turret wall, while the photo on the right shows the modification installed on the exterior. The "turret patch" consisted of two castings welded together in the middle as seen here. Each casting is listed as having been 1 1/2 inches thick.

Pistol port closed

Heretofore, all 75mm turrets were cast with a pistol port on the left side towards the rear (left-side photo). However, in April 1943 the Ordnance Department determined that the pistol port was a ballistic hazard and called for its elimination. Consequently, the D50878 turret was redesigned without the pistol port as shown on the right.

Turret cheek armor

As part of the same redesign, the "thin spot" was remedied with what modelers call the "cast in, thickened cheek" on the right front (circled in red in the left side photo), thereby eliminating the need to weld on the turret patch. The extent of the "bump out" of the "cast in, thickened cheek" can be seen right where "Cornouailles" is painted. Pierre-Olivier photographed the interiors of a few no pistol port, "cast in, thickened cheek" D50878 turrets and as can be seen in the photo on the right, the armor surface is flat with no scooped-out areas. There does appear to be a little outward bulge. This leads us to think that the armor in this area of the turret shell was actually moved out a bit to give the operator room to work the traversing mechanism without scraping his knuckles on the turret wall. On the exterior, we suspect that the protruding part of the turret casting was not really "thickened" but was intended to maintain the as designed armor basis of 3 inches on the front and 2 inches on the sides. We have no way of measuring this, but if we are right, the useful descriptive term "cast in, thickened cheek" would be something of a misnomer.

One of the interesting historical anomalies of French Lend Lease Shermans, is that some are noted with the unnecessary application of the "thin spot" patch on no pistol port, "cast in, thickened cheek" D50878 turrets. "Valois", "Massaoua" and "Chemin des Dames" are surviving examples. The patch consisted of two cast sections, and the pieces were not made to fit the contours of the revised turret. Consequently, the patch was ill fitting with a noticeable gap between the two sections. The surviving French 2nd Armored Division veteran M4A2, "Massaoua" above shows a particularly poor fit. Lack of direction from US Ordnance personnel, and/or simply a language barrier misunderstanding were the likely culprits in the case of the unneeded turret appliqué.

Pistol port welded

The "no pistol port" turrets began to enter the production lines in the summer of 1943, but in the meantime, factories and depots were directed to weld up any remaining pistol port turrets that were in the pipeline. The "window" where turrets were welded up appears to have run from about May to September 1943, even though the pistol port was "reinstated" on 23 July 1943. Of course, not every pistol port was welded up. During this period, inspectors at factories and depots reported incidences of Shermans passing through with working pistol ports. Counting heads suggests that, in most cases, the pistol port itself was used as the "blank off" with the hinge barrels on the casting burned off or otherwise removed. This may have been to ensure a watertight seal. The pistol port was then welded on, both outside and inside. The photos above show a typical job on the unusual "half a tank" monument in Wibrin, Belgium. This M4 appears to be a US Army WW II battle casualty. The Serial Number is not known, but the appearance suggests it would have been accepted at ALCO in July or August 1943. For what it is worth, the turret was cast by General Steel-Eddystone and is serial number 3663. From "counting heads," we believe this turret would have been cast in late April or early May 1943. Based on the similarity of the welded-up pistol port to a few other GS-E turrets, we wouldn't be surprised if the weld up job was done at Eddystone before the turret was shipped out.

Pistol port welded

Pistol ports were welded up in a number of different ways. Here we present two somewhat common examples. The left side photo shows the welding technique typically noted on Chrysler M4A4s. On the right we have a method where the center hinge holder (1) was ground down and the pistol port casting was welded on in such a way that it stood out a bit. This particular job is on a General Steel-Commonwealth turret with a casting date of "4-43" [April 1943]. Despite the unpopularity of the elimination of the pistol port, it is evident that the majority of US Army M4 and M4A1 75mm Shermans that fought in the Normandy Campaign and beyond had either welded up or no pistol port turrets.

Pistol port welded

This Signal Corps photo is dated "24 July [1944]...near La Commune, France." It demonstrates how, without the pistol port, it often took three men to load ammunition. A man on the ground passed rounds up to a man standing highly exposed on the tank, who passed the rounds through to a man in the commander's hatch. Only one man on the ground, and somewhat protected by the tank, was needed to pass ammunition through to a man at the pistol port. This M4A1 can be seen as USA 3036927 indicating that it was produced by Pressed Steel Car in May 1943. This appears to be a case where the actual pistol port casting was not used to blank off the opening. A beveled piece of armor seems to have been employed instead. The inset shows a similar application on a surviving turret cast by Union Steel, PSC's main supplier of turrets. Some motion picture footage taken in Normandy shows that USA 3036927 was a dozer tank named "Marauder" probably of the 2nd Armored Division.

Late low bustle

The feedback from the using arms concerning the elimination of the pistol port was so negative, that in July 1943, Ordnance voted to reinstate it. Feedback also stressed the need for a loader's hatch, so once again, the D50878 turret was redesigned to include the pistol port as well as introduce the "oval loader's hatch." These turrets continued to have the "thickened cheek" on the right front (all the items circled in red on the photos above). Pressed Steel Car seems to have been the first manufacturer to introduce the D50878 turret with loader's hatch in late October 1943. The first ones were low bustle turrets like the one shown above. As Fisher-built M4A2s pretty much disappeared to Lend Lease (hence some difficulties in photo and surviving vehicles study) , we can only observe that the oval loader's hatch appears to have been introduced on M4A2(75)s very late in 1943 or early 1944. There are a few pictures of Soviet big hatch M4A2(75)s with low bustle turrets with loaders' hatches, which are presumed to be D50878s.

Hatch

The commander's hatch was improved with the introduction of "turret hatch D69993 with equilabrator." The hatch hinges were equipped with integral springs (1) which made it easier for the crew to open and close the heavy hatches. It is assumed that a more robust internal locking mechanism was included with the new design, since the external hatch locks (circled in the photo of the older model on the right) were no longer installed. The redesigned hatch was released as a "critical modification" with "No tanks without this item to be accepted after 11/8/43 [8 November 1943]." We can't confirm if the freeze date was absolute, but we can observe that many Shermans produced in late 1943 are seen with the new hatches. Of course, the design carried over to the D78461 high bustle turrets when they were introduced starting in late November 1943.

Chart

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"High bustle" turrets - From the D50878 turret to the D78461 turret

Late "High bustle" 75mm turret (part number D78461)

High Bustle turret

As supplies became available in late 1944, 75mm turrets were factory equipped with the commander's vision cupola (left side photo). Modification kits were also supplied for retrofit. Late high bustle D78461 turrets have a bulge to better accomodate the commander's vision cupola (right side photo). This modification seems to have appeared on turrets cast from November 1944 onward.

Recycled "Low bustle" turrets

Recycled low bustle turret

Due to the critical foundry situation, Fisher Body agreed to accept 300 used D50878 turrets left over from the retriever conversion program. They were to be updated to current standards, with M34A1 gun mounts & turret patches where needed. A loader's hatch was to be cut in. They were to be installed on large hatch M4A3(75)Ws at the rate of 100 per month starting in November 1944. There are a number of period photos of these, including some tanks with HVSS. Most or all of them appear to have been equipped with the commander's all round vision cupola. Perhaps a small number of them saw some combat in the ETO in the closing days. It's common knowledge that the low bustle turret caused some interference issues when mounted on a "big hatch" Sherman. However, that didn't seem to have been a problem with all the low bustle, no pistol port turrets on many M4 Composites. In any case, the Fisher docs mention that the recycled turrets "would require flame cutting of some stock on the lower rear corners of the radio bulge to eliminate interference with the drivers' doors". These photos of a 1942 production Union Steel turret (S/N 871) that was certainly recycled show hints of how some material was removed from the bottom corners of the turret bustle. The loader's hatch was also neatly welded in.

It is thought that some more low bustle bustle turrets received the same upgrade in the early 1950s. In that case, the 75mm gun was replaced with a 76mm. These "upgunned" Shermans were sent out as Military Assistance.

Recycled low bustle turret

The way to distinguish between a recycled D50878 turret & a late 1943 production D50878 with low bustle and loader's hatch is that the late production will have a cast in thickened cheek, whereas the recycled turret will have the armor patch on the right front (as shown above). Also if the serial numbers can be read, the recycled turrets will have much lower serial numbers than the late productions ( the few late production turrets identified have S/Ns in the 4000 & 5000 range).

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