Applique Armor on M4 series Medium Tanks By Kurt Laughlin The US Army produced several appliqué or add-on armor packages for the M4 series of medium tanks during World War II. These packages gave additional protection to the driver’s hoods on the glacis, the hull ammunition racks, the turret side, and the gunner’s direct sight telescope. The shape, location, and applicability of this armor are frequently puzzling to modelers. This article is based on several contemporary sources such as Modification Work Orders (FSMWO), Field & Depot Issues (FDI), Ordnance Department drawings, and production records, as well as modern “field and photo work”. Thanks to fellow Sherman enthusiasts Mike Canaday, Joe DeMarco, and Mike Foncannon for help in preparing this article. “Small Hatch” Vehicles Appliqué armor was predominantly used on the earlier “small hatch” or 57-degree glacis tanks. The four issued kits were applicable to virtually all of these vehicles but actual installation was far less common. Once a vehicle was issued to the troops – either stateside or overseas – it was rarely modified. Most, if not all appliqué appears to have been installed by the factories or by the tank depots before issue or during a remanufacturing program. Turret The front quadrant of the D50878 “low bustle” turret was designed with a uniform 3 inch thickness except for the right front where two cuts were made to clear the turret traversing gear. These cuts reduced the armor to 2 inches creating an obvious weak spot. In production the contour was changed to move the right turret wall outwards 1 inch so that a uniform wall thickness could be maintained. The thickened turrets started appearing in April of 1943 and were in general use by August. To update the turrets already produced, FSMWO G104-W57 of 14 June 1943 had instructions for adding two plates to the front right. The sketch below is a development or flat pattern of the appliqué. The actual plates had a curve in them to match the turret and the upper right corner of the front plate was folded over the front of the turret. Although not shown, the upper left corner of the side plate had a 3 inch radius and a 2 inch radius on the

lower corner. The plates were 1-1/2 inches thick when made of rolled plate and 1-3/4 inches thick when cast. They were to be welded only on the top, center, and sides with the bottom unwelded. Surviving examples, however, show that these instructions were frequently ignored and the bottom edge completely welded.

Note that the final layer of vertical welds was applied horizontally rather than along the length of the side. This is a typical practice indicating that the weld – and the plates - was probably attached with the turret in its normal orientation. The full weld on the underside means that the turret wasn’t mounted on the tank because the bottom edge is blocked by the splash guard ring. With two types of appliqué and as many as nine foundries producing turrets the fit between the plates and casting was unlikely to be close. The work order

advised that weld metal should be applied to the inside of the plates to get a good fit (less than 1/8 inch gap) with the turret. Although the plates were supposed to be attached 4 inches above the bottom edge of the turret (leaving around ¾ inch between the ring and appliqué bottom) it seems that in many cases this was interpreted as 4 inches above the turret race splash guard ring, as seen in the extreme example below. This may also be the result of attaching the plates with the turret still mounted on the hull and locating the appliqué to give access to the bottom for welding. For whatever reason, this error negated the purpose of the appliqué in the area immediately above the turret ring, the place where the original armor thinning was greatest!

Hull Sides Early vehicles stored ammunition in simple racks in the hull sponsons. The rupturing of the cartridge cases and the ignition of the spilled powder propellant was considered to be a major factor in the reputation of the M4 to burn upon projectile penetration. FSMWO G104-W81 of 6 August 1943 provided a “quick fix” to the problem by armoring the hull racks both inside and out. (This article limits itself to the exterior modifications.)

Three 1 inch thick plates were added to the hull sides, two on the right and one on the left. The forward plates on both sides were identical. The plates were mounted 1 inch above the bottom edge of the sponson and located off the turret centerline as shown.

The placement of the right front plate caused the upper right corner to overlap the hull side to glacis weld. On some tanks this corner is clipped so that the plate clears or nearly clears the weld. Similarly, the bottom edge is fully welded on some examples and merely tack welded on others. Those with full welds typically have beads that follow the plate perimeter while those with tack welds on the bottom have horizontal layers on the vertical edges. In line with normal welding practice the all-around weld arrangement is consistent with installation while the upper hull plates were still in pieces and lying flat. The three-sided weld arrangement would be expected from installation on an assembled hull or tank. The clipped corner information is not definitive but it may indicate appliqué installed before hull assembly as well. On M4A3s the clipped appliqué plates overlap the glacis weld by about ½ inch and the “clipped” edge is 3 inches long. M4s frequently carry plates that are 6 inches along the angled edge and clear the weld completely.

Obviously, mating flat plates on the irregularly curved cast hull required additional measures. While still located 1-inch above the sponson edge, the FSMWO directed that the plates were “cut to suit”. Photographs show several variations in the cut configuration. The left and right rear plates were normally split near the top while the right front plate was cut into two to five pieces to match the compound curves in this area. At some point formed plates that better conformed to the cast hull were issued but the introduction date is unknown.

Late in the small hatch M4A1 production run the upper hull casting was altered to thicken the sides rather than weld on appliqué. The thick regions were in the same locations and thickness as the appliqué but were a bit wider to account for the blended transition to a thicker hull side. Also, the area between the two right side thick regions did not drop down to the original size but remained about ½ inch thicker than normal. A related issue involved the attachment of sand shields to strips welded on the bottom sponson edge. The normal sand shield attachment strips were 2 inches wide while there was only a 1 inch gap below the appliqué plates and above the sponson edge. This was perfectly adequate as the strips were to over hang the bottom sponson edge by an inch to allow fastening of the sand shields themselves with a bolt and nuts. On survivors it appears that more than a few required some ad hoc modifications to the strips to fit them below the plates. Some M4A3s even had the appliqué plates mounted about an inch higher than normal, apparently to clear the mounting strips that had been welded first. Hull Glacis The nearly vertical front face of the driver’s hood was a definite weakness in the M4 design. On 23 August 1943 FSMWO G104-W83 was issued “To install hatch guards for improving the ballistic qualities of the armor plate in front of the driver’s and assistant driver’s hatches.”

These plates were 1-1/2 inches thick and installed as shown above. The top edge was to be placed approximately 2 inches below the upper surface of the hood casting (although many are nearly flush) and centered in front of the hatch. On tanks fitted with a canvas cover fastener ring around the cal. .30 MG, the top of the ring had to be cut loose from the hull and bent up, then reattached to the appliqué plate.

Note that this modification was not limited to direct vision tanks but for all that used the small hatch hoods with vertical fronts. Curiously this FSMWO applied only to M4 and M4A3 hulls. (The M4A1 hull was considered to be “adequately” shaped already.) The omission of M4A2s and M4A4s may indicate their status as primarily training or International Aid models. M34 Combination Gun Mount Troop trials indicated the need for a direct sight telescope as an alternate to the periscopic gun sight in the M34 Combination Gun Mount. The M34A1 mount standardized in October 1942 began replacing the M34 in March and April of 1943. There were, however thousands of M34 mounts still in existence that required modification. Ordnance Department officials chose – for reasons that remain unclear – to modify the mounts via a Field & Depot Issue rather than a FSMWO. FDIs were production control documents generated and issued directly by Ordnance’s Tank-Automotive Center in Detroit, Michigan rather than through the War Department in Washington, D.C. FDI 289, dated 13 December 1943 addressed the change to the M34 mount. The work of interest to modelers included slotting the right side of the D50880 gun shield as an opening for the sight; welding the semicircular D52870 shield to guard the slot; removing the right shield lift lug and replacing it with a threaded hole and plug for an eyebolt; adding an elevation stop to the gun shield; and welding the D52869 shield to the D51288 rotor shield. Interestingly, this modification was to be applied only to overseas and overseas bound tanks, yet few photographs of the modified M34 mount in service have surfaced. Preference seems to have been given to direct replacement with the M34A1 mount. This configuration has survived on many of the stateside training vehicles (mainly M4A3s) remanufactured in 1944-45.

Above is an overhead view of the modification. Note that the left side of the mount was unchanged. The picture below shows details on the right side. A – Threaded hole and plug for eyebolt; B – Scar from removal of lifting lug; C – Slot in side of D50880 gun shield; D – Elevation stop; E – D52870 shield; F – D52869 shield.

“Large Hatch” Vehicles One goal of the 1943 M4 redesign was to reconfigure the ammunition stowage and armor arrangement to reduce its vulnerability. As such, most large hatch or 47-degree glacis tanks did not use appliqué armor but those vehicles built during the transition to water protected racks did. None of these vehicles required the

hull glacis appliqué nor used the M34 mount so these modifications were not applicable to these tanks. Also, the D78461 “high bustle” turrets were specifically designed for use with large hatch vehicles and included a re-contoured right side. It appears that most of the large hatch tanks used this turret. There were, however a number of large hatch hulls that did mount appliqué: M4: Detroit Tank Arsenal built 1676 75mm gun tanks in late 1943 and early 1944 with cast hull fronts and appliqué on the hull sides. The appliqué was “clipped” on the left side to clear the glacis weld while the front right plate was cut almost diagonally to allow it to lie against the casting. The upper right corner was also clipped. (Some early tanks were actually small hatch hulls but still used appliqué.) M4A1: The last of 500 or so 75mm gun tanks built at Pressed Steel Car in 1943 were large hatch hulls with thickened sections where the appliqué plates were normally located on small hatch vehicles. Most of these were converted to Duplex Drive tanks. The thickened sections were well blended into the other armor and ran full thickness to the bottom of the sponson with a sharp edge. The area between the two thick sections on the right side was also about ½ inch thicker than normal. M4A2: Fisher Tank Arsenal produced 289 large hatch M4A2s with appliqué plates in early 1944. Placed at the same locations relative to the turret centerline as the small hatch tanks, the front right plate cleared the glacis weld and did not require clipping. M4A3: Some photographs exist showing M4A3(75) (Wet) tanks with D50878 turrets mounting appliqué and M34A1 gun mounts. These turrets may have been mounted on an expedient basis when the D78461 turrets were in short supply. A February 1945 document refers to “salvage” turrets available for new production which may be older turrets removed from gun tanks converted to M32 tank recovery vehicles. M4A6: The 75 M4A6 tanks used essentially the same glacis castings as the Detroit M4s produced at the same time and were similarly armored. As a final note, the observer should not assume that a tank sporting appliqué is a “remanufactured” vehicle. Remanufacturing, to use the term narrowly, refers only to those 5,434 worn out training tanks completely rebuilt to a “like-new” status from December 1943 to mid-1945. As explained above, appliqué was frequently installed before the tank was ever issued to a soldier, and sometimes before the tank was even complete. Hopefully this information will help modelers in an area that has not been well documented to date and has even caused confusion with some kit companies –

despite what the instructions may say, M4A3(75) (Wet) tanks did not have hull appliqué!