- Yes
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Overview
The M9 GMC was a prototype tank destroyer based on the M3 Lee mounting a 3in M1918. 50 were ordered in 1942, but this order was subsequently cancelled as the superior M10 was already entering production.
History
Origins
The Tank Destroyer Command was established on December 1st 1941 in response to the German blitzkrieg. The Tank Destroyer doctrine involved special units of mobile, well-armed armoured vehicles being called to stop any enemy breakthroughs, allowing the traditional tanks to focus on offensive maneuvers.
The first tank destroyers, the M3 GMC and M6 GMC, were simple conversions mounting a field gun on the vehicle that typically towed it, thus providing slightly better mobility. These designs were simple and cheap but didn’t offer the performance necessary to combat the ever-improving German armour. So, an order was placed for the development of a tank destroyer based on the M4 Sherman armed with a 3-inch anti-tank gun in a fully rotating turret, what would become the M10.
The T24
As soon as development of the M10- then called the T35- began, there were concerns that it wouldn’t be ready for some time, leaving the US without an effective tank destroyer. An interim design program was initiated aiming for a simpler casemate mount, similar to how the interim M3 had its main gun in a sponson to speed up development and production while the M4 was still unfinished. This vehicle was designated the T24 and featured a 3in M5 anti-tank gun on an M2A2 mount essentially just sat atop an M3A2 hull. This vehicle came with numerous issues: it had extremely limited elevation and fell far short in depression, provided essentially no protection to the gun crew, and was excessively tall. That last weakness would be particularly troublesome as the T24 would likely be seen by enemy forces before the T24 spotted them, defeating the purpose of a tank destroyer. The T24 was deemed unsatisfactory and in January 1942 was sent back for improvements.
The T40
The next prototype was designated the T40. It was a rebuild of the T24 using the same hull. The T40 redesigned the gun mounting, cutting down the hull to place the gun lower in the vehicle. This simultaneously addressed the issues of silhouette, gun elevation limits, and crew protection. The M5 was replaced with the older M1918 anti-aircraft gun, with the idea being that as the M1918 was phased out of its primary role there would be an excess to be used for T40s. This turned out to be untrue. The single prototype underwent trials in early 1942, being standardized as the M9 GMC on April 30th. An order for 50 was placed, but this was reduced to 28 when it was discovered that there were only 27 spare M1918s. Such a small order would mean a very high cost per vehicle, and the T35E1 had been approved for production and standardized as the M10 in May and June 1942. Always intended to be a simple interim vehicle, it didn’t make sense to produce the M9 when the M10 was ready for production. As such, the M9 was cancelled in July with no further vehicles built.
Specifications
General
Length excluding gun: 5.68m
Height: 2.3m
Width: 2.73m
Weight: 24.1 tonnes
Armour
The M9 has the armour of the M3 hull it is built on, with a relatively short thinly-armoured open-topped and mostly open-backed casemate on top.
Hull front: 38.1-50.8mm
Hull sides: 38.1mm
Hull rear: 38.1mm
Hull roof: 12.7mm
Superstructure front: 50.8mm, 30 degrees
Superstructure sides: 25.4mm, 0 degrees
Superstructure rear: 19.1mm, 0 degrees
Superstructure roof: none
Armament
The M9 is armed with the 3in M1918 anti-aircraft cannon. This cannon dates all the way back to WWI. It fires the same ammunition as the later 76mm M7, though at a lower velocity of 732m/s for AP rounds due to its shorter barrel. While this is lower than the 792m/s of the M7/M1, it’s still much higher than the 618m/s of the 75mm M3. Performance would likely be most similar to the KwK 40 L43, which fires a slightly lighter shell at slightly higher velocity.
76mm L40 M1918
40 rounds
Max 8 RPM (7.5s)
M79 AP- 732m/s
M62 APHECBC- 732m/s
M42 HE- 788m/s (est)
10/27 degrees left/right, manual
+29/-8 degrees elevation, manual
Mobility
Mobility is very similar to the M3 Lee. However, the M9 is significantly lighter.
R975-EC1, 400hp
40/4 km/h in forward/reverse
24.1 tonnes
16.6 hp/tonne
The M9 in-game
The M9 GMC would be a perfect little BR 2.7 tank destroyer to fill the gap between the M3 and M10. It’d be very comparable to the Archer, Su-57D, and Marder IIIs. Frontal armour would be rather effective, especially on the lower half where the M3 hull is unaltered. However, the M9 would still be extremely vulnerable to overpressure, artillery, aircraft, and flanks. Mobility would be unremarkable, with the M9 being much slower than the many zoomy light tanks around the BR, but faster than most tank destroyers, heavy tanks, or even many mediums. While the M1918 doesn’t have quite the power of the later M7 and M1, firepower would still be excellent for the BR, with the only vehicle the M9 might struggle to penetrate being the KV-1 L-11.
Gallery
Side view of M9 at maximum elevation
Front and rear view of the M9
The T24 was much taller than the M9, as can be seen in the photos above
The M1918 in its original role as an anti-aircraft cannon