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Grant, Vehicle OM1-OM2 values


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#1 Peter M. Skaar

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Posted 26 October 2024 - 09:58 PM

Having played a bunch of Desert War games over the last couple of years, I just recently added some Grants to the mix.  Overall I don't have any issues with stats but it seems that the Grant has some really low OM1 and OM2 values for the 75mm gun making it quite ineffective in a tank on tank engagement.

OM1 value is -4.  OM2 value is -7.  I know that the sponson arrangement for the main gun was not as good as having a 360 degree rotating turret and that makes it almost more of an assault gun in some ways.  This seems a bit high negative to me but I am curious as to how this particular stat was determined.  My data book is from 2006 so if anything changed I don't have it.

Looking at the StuG IIIG, a true assault gun, the OM1 is 0 and the OM2 is -3.  The Panzer IVF1 with the L24 is OM1 of -2 and OM2 of -5.

I know a lot of things go into these stats so I am not saying they are necessarily wrong for the Grant but they seem more negative for the same basic gun as the Sherman.  Your thoughts on this?

 



#2 Kenny Noe

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Posted 27 October 2024 - 09:25 AM

The British had two (2) distinct camps in military doctrine {possibly more} in the late 1930s and early 1940s when it came to the utilization of armored vehicles.   One (1) was Infantry Support (slow, anti-fortifications)  and the other two (2) was Cruiser (fast mobility, deep thrust).  Early war thinking.

 

Re: the Grant.  My understanding from various reading was the Grant was designed to be an infantry support platform first and foremost.  The 75 was primary for shooting HE at infantry and fortifications and the 37mm was a defensive weapon that could take on Pz I and IIs.  However, lessons learned in 1941 and 1942 desert actions against Pz III and IVs made it was fast apparent that the 37mm cannon was obsolete.  So the 75 cannon was given the AP round which would penetrate the enemy tanks.

 

The 75 had a very short barrel and poor fire controls thus the dismal OM123 numbers.  Killing the latest  German tanks in the desert wasn't the problem, it was hitting them.   

 

After Kasserine the British swiftly moved away from the Infantry Support doctrine to lend lease Shermans as fast as they could.  

 

I'm sure others could give more technical guidance on the Lee/Grant fire controls.  But in MP stat terms the short barrel is a major factor when deriving the OM123.

 

But my 0.02¢ is that you cannot compare combat effectivness of a Lee/Grant to a Sherman although both had the same transmission/ engine and fire a 75mm cannon.



#3 Kenny Noe

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Posted 27 October 2024 - 09:29 AM

If you have registered your databook, then you can DL all updates for free.  You then can be assured that even though you purchased the book in 2006 you will have the latest revisions.



#4 Phil Callcott

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Posted 27 October 2024 - 12:32 PM

Hi.

 

Grant was designed to be an infantry support platform first and foremost. 

With respect, it was not.  It was to be a medium tank, the hull 75mm position was chosen because US industry did not yet have the experience to make a turret to fit it in.

 

The 75 was primary for shooting HE at infantry and fortifications and the 37mm was a defensive weapon that could take on Pz I and IIs. 

Both guns were fitted with gyro-stabilisers to enable firing on the move.  Both had AT and HE rounds.

 

The 75 had a very short barrel and poor fire controls thus the dismal OM123 numbers. 

The original gun had a 31 calibre long barrel,  Why are the Grant's sights so poor, both the 37 and 75 mm had their own periscope sights?  And stabilisers as previously mentioned.

 

In MP stat terms the short barrel is a major factor when deriving the OM123.  But why?  British 25 pdr gun howitzers with a 28 calibre long barrel and limited traverse had no trouble hiting enemy armour, and knocking it out.

 

After Kasserine the British swiftly moved away from the Infantry Support doctrine to lend lease Shermans as fast as they could. 

No they did not, Churchills fullfilled the heavy infantry support role when fitted with large mortars, flamethrowers and 75mm guns.  75mm Cromwells for fast recce were alongside Shermans, the Comet arriving too late to make much impact.

 

Finally, historically the Grants were effective in battle, https://warfarehisto...nt the “Pilot.”



#5 Peter M. Skaar

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Posted 27 October 2024 - 02:47 PM

Thank you both, Kenny and Phil!  I appreciate the input.  I do think the Grant is a bit more effective than the stats would indicate and that is why I asked the question but the truth is, I don't really know for sure other than gut feeling so I am prepared to learn things.



#6 Mark 1

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Posted 18 December 2024 - 06:24 PM

A bit late to this particular party, but I second much of what Phil has said above.

 

US Army Ordnance did not design tanks with an "infantry support" role in mind. That approach was not in their thinking. The US Army perspective was that tanks were machines that should be mobile enough, have sufficient protection, and sufficient firepower, to achieve their doctrinal missions.  The doctrinal missions of medium tanks were first and foremost offensive in nature ... to carry the fight to the enemy in combat on the forward edge of battle against whatever forces would oppose them, to exploit front line advantages by deep penetration into enemy rear areas, and to be the first counter-force against enemy armor in their areas of operation.  It was explicit in the Field Manuals of the armored force that the priority of US medium tanks would be to defeat enemy armor whenever it was present in their area -- that is to say they were expected to drop whatever else they were doing to defeat enemy armor first.

 

More specifically in regard to the M3 Medium (Grant and Lee), when it was designed there was a recognition of the success of the Pz IV in France, driving a sense of need to get a 75mm gun onto a medium tank. The development of (what would be) the M4 actually started first, but was put on hold when it became evident that the milling of turret rings and the casting of turrets large enough to support a 75mm gun would not be within the capabilities of several of the current manufacturers, which would delay and limit production. So a stop-gap solution would be to mount the 75mm gun in the hull, and mount the 37mm gun in the turret.

 

It was indeed expected, at that time, that the 37mm gun would be the tank's principal anti-tank weapon, and the 75mm hull gun would be for engaging emplacements and other defensive works that were not vulnerable to the (MANY) machine-guns, which were otherwise the principal anti-infantry weapons. But that's not to say that the 75mm would not be used against tanks -- only that it was thought that the 37mm would be adequate for AT work (surprise!) and would be quicker on target and faster to fire. Both were expected to be usable during mobile action -- again the doctrine was offensive in nature and emphasized firepower and maneuver. The early US Armored Force was really big on cavalry-style charges right into the heart of enemy positions. One need only look at the actions of the US 1st Armored Division around Sidi Bou Zid to see how that doctrine worked, or did not work (even using M4 Shermans).  Usually the tanks would fire from short halts, but the stabilizers were there to help get on target quickly at the moment of a short halt, despite the rocking of the chassis and the undulations of the terrain.  There was indeed a sort of "walking fire" concept as well, but that was expected to be more of suppressive fire than actual destruction of identified targets.

 

I would expect (here it is my opinion, no stats or historical evidence to cite in support) that the 75mm hull gun would be as effectively served as the 37mm gun, given each had their own crews.  The 37mm, due to its higher velocity, would have a bit of an advantage in accuracy against a moving target or where range was not precisely known, but it lost velocity faster so once the range estimation became a real factor they were probably almost equal. All of that, though, would be limited to targets within the 75mm gun's arc of traverse. Once the gunner had to get the driver to traverse the hull to get his gun on target, all bets were off. StuG crews were drilled in this, but I've not seen any indication that M3 crews (at least US crews) trained and practiced this much if at all.

 

-Mark

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