22 replies to this topic

[Dan Lewis]

Hi Guys, 

 

Why is the 75mm M2 gun on Grant have an OM1 of -5 and the same gun on the Sherman is a -1. I know that the Grant tank has a limited arc due to hull mounted gun, but that to me means that they can't target vehicles that are on their left side. If the target it to the right front would it not have a similar to hit chance or is there something else impacting the calculation?

[Kenny Noe]

Dan,

 

Hi.  The Lee / Grant 75mm only had a 32° L/R traverse so basically the tank had to spin on it's tracks to engage a target on the left or right "sides".

 

I've dropped a note to Bob.  He should resurface by this weekend (his work weeks are long) and give a more comprehensive discussion.

 

Thanks for the thread.

[Dan Lewis]

I found a better picture of the Grant/Lee without the canvas dust protector over the gun. I Didn't realize the gun slot was fixed,  I thought there was some type of rotation similar to a turret. So that 32 degree must be the ability of the gun to move 16 degrees to either side of the port from within the tank, kind of like how a machine gun can rotate the barrell even though the hole doesn't move. 

[Bob Benge]

All of the guns in Mein Panzer are based of the same formula. The stats are not based on the gun itself but other factors that tie together to give a gun system. The Mein Panzer gun system OM1/2/3 ratings are based on a fomula with standard values that are based on a number of factors which  include:

• stabilization type
• turret traverse
• fire control
• actual rate of fire
• barrel length

Each of these factors has a varied number of types that have values associated with them. With that in mind, I think you will notice that there is a significant differences between the Grant and Sherman gun systems. Example: Grant has no gun stabilization and manual limited traverse (approx. 15 degrees to eash side of center) and the Sherman has Y-axis stabilization and hydraulic or electric/manual turret traverse. and whil I can see the arguement that crews turned off the stabilization I will provide this...

 

"Interestingly, while the technology was there, many crews didn’t use it effectively due to limited training or maintenance issues. Some even disabled it altogether. But for those who did use it properly, it offered a real edge in mobile engagements."

 

I hope this sheds some light on the subject.

[Peter M. Skaar]

I had the exact same question a few months ago on this forum.  I still feel the 75mm gun is way undervalued in its ability to hit on OM1 and OM2.

I went back and looked at the Data listings for various assault guns - German and Russian.  These are also guns with a very limited traverse.  OM1 on even the shell lobbing StuGIII A-E is only -2.  This is the short 75mm gun.  It has the same OM1 as the StuG IIIF in one listing although in another listing the StuGIIIF has an OM1 of 0 along with the StuG IIIG.

The various Russian assault guns show -3 up to +1 on OM1.  

I feel that -4 to hit on OM1 and -7 for OM2 for the Lee/Grant 75mm gun just seems a bit harsh based on the other vehicles that are dealing with the same issues.  I know a lot of research went in to coming up with the stats for this game and and I do appreciate the work.

 

[Dan Lewis]

Well based on this picuture the gun has no left right traverse at all, and can only raise or lower the gun to affect distance/range. So the only aiming mechanism from a field of fire is rotating the tracks of the tank. Which means it sucks as an anti-tankgun. So now I think the OM is fully deserving. I could be wrong here, but doesn't look like it can traverse to me. 

 

Attached Files

•  Lee.PNG   636.76KB   1 downloads

[Kenny Noe]

The lack of stabilization and 360 turret traverse really played havoc with the final stat numbers vs the same gun on the Sherman.

 

However, the beauty of MP once you understand the reasoning of the OM 1/2/3 numbers there's no law saying you can't change to numbers for your scenarios.  Just remember, official MP Stats have the same algorithms applied to all weapon systems.  So be careful not to over power a weapon system to you're belief and then get frustrated because the game now seems out of balance.

 

We've had folks in the past rant and rave that the game stinks because "battles" don't come out to expected results.  Only after clarifying questions is it revealed the there was a stat change.  Then the individual gets mad that "all" the stats are bogus.  (His opinion and one he'd entitled).  But you have the power to change.

[Dan Lewis]

I will say however after running Beda Fomm Scenario, Italians, with M13/40, couldn't qualify to hit unless they got real close. OM of -4 was brutal. I thought maybe that was unfair, so I looked up the percentage chance to hit with this gun from one source, and was surprised that yeah % hit is pretty poor, still based on this source, a -3 might have been more accurate as OM1. If I run it again, I'll use OM1 of -3, but it shows that -4 in MP chart is reasonable conclusion. It just means it sucks to be the Italian army commander. 

[Dan Lewis]

Here's anothe image from a production line for the tank showing the port without the gun being installed. Again, doesn't appear to be any left/right traverse mechinism. Looks to be a fixed mount. 

 

Attached Files

•  grant 2.PNG   628.52KB   1 downloads

[Peter M. Skaar]

Hi Dan

I did some online research on the traverse for the 75mm main gun.  I even saw the FM on line about the M-3 Lee regarding traverse.  The gun could traverse 14 degrees  to the right or the left for a total of 28 degrees.  This, in my opinion puts it in the category of assault gun which I have already mentioned in my earlier post.  Personally, I would put the OM1 rating at least -2 and maybe even -1.  

One other downside to the hull sponson layout is that the vehicle cannot actually shoot the main gun from a hull down position.  This should be factored in when playing a game.

For a couple of months in 1942, the Grant was considered the overall best Allied tank in North Africa until the advent of the Sherman in October 1942.

[Dan Lewis]

Thank You Peter, usefull feedback...so yes, given a bit of traverse I think -2 is reasonably fair. I played a game few years back with Grants and they were miserable in terms of getting any hits on Germans. Any gun with a -4 is really handicapped in Mein Panzer. 

[Peter M. Skaar]

I totally agree with you on that point, Dan.  I think in future games I will go with -2 for OM1 and maybe -4 for OM2 on the Lee/Grant.  Most of the time, I have no issues with the stats as given but this was an exception.  As given, the OM1 and OM2 stats really punish the Lee/Grant especially compared to similar assault guns.

[Mark 1]

Here's anothe image from a production line for the tank showing the port without the gun being installed. Again, doesn't appear to be any left/right traverse mechinism. Looks to be a fixed mount.

 

Dan -  I am afraid you are not correctly interpreting the pictures you have recently found.

 

I can assure you that the 75mm gun in the M3 Medium tank (Lee/Grant) did in fact traverse left and right.

 

I have been fortunate enough to crawl over many WW2 tanks in various states of dereliction or restoration.  Included was one M3 Lee.

 

In this case I didn't get many pics (and none from the inside, which was in quite a sorry state to be honest).  However, I can assure you that there is a traverse mechanism (hand cranks) that did work, even in the case of this vehicle in an un-restored state.

 

And yes, decrepit or not, displayed for the public or not, I have climbed into any number of rust hulks just for the fun of it (and the research).  Here shown in an M4A3E2 Jumbo Sherman in the LST building on Ft. Knox many years ago. 

 

So I offer my assurance, as one who has actually laid hands on the gun-traverse mechanism, that the 75mm gun in the M3 did traverse left and right.  Which is a good thing, because unlike the German StuG crews, US M3 Medium tank crews did not train for the driver to adjust the facing of the vehicle for the sake of helping the hull gunner to track a given target.  US tanks did not have a pivot-in-place capability, having only a single gear for both tracks, with levers for differential braking, and the accelerator pedal, for turning (meaning the tank would have to move forward or backwards with one track braked to change facing). Drivers (at least US Army drivers) did have some level of training to do some turning while advancing on a target to adjust the fixed hull MGs, but that was for directing streams of suppressive fire rather than for hitting specific targets. Beyond that, the driver was trained to take direction from the tank commander in the turret, not from the gunner in the hull.

 

If you'd like further evidence of the left/right laying of the gun, I can also offer this link to a Chieftain's Hatch video:

 

Haven't had a high success rate in posting links to YouTube vids in this forum, so if you don't see the link, just go to YouTube and search for: "Chieftain's Hatch M3 Grant" and you'll find two vids -- you want the pt.2 vid (pt.1 is the outside of the tank, pt.2 is the inside).  It's one of his earlier videos, so there's lots of smaltzy musical cut sequences if you watch the whole thing. If you prefer, go straight to timestamp of about 18:30 for the part on the hull gunner's position. He even describes the traverse as specified in the field manuals for both the M3 Medium tank and the M2 75mm gun, which were part of his research in preparing for the video.  (His videos typically involve a fair bit of pre-work and research, which may not be well known by his audience. While not involved in this video, I did research for a few of his other early videos. I have, over the years, spent a fair bit of time doing primary research and going into archival docs -- probably several multiples more time than I've spent climbing over and in tanks...).

 

Hope that helps.

 

-Mark
(aka: Mk 1)  

[Peter M. Skaar]

Hi Mark

The question I have for you, based on what you know about the M-3 Lee/Grant main gun is this - Do you think the To Hit stats are correct (good) as given?  

After Bob B. weighed in on this a few posts ago giving the criteria that go in to the stats as listed, I went back and checked the stats for other assault guns/tanks that have main guns without full traverse.  I know not all of these are equal but it seems that the Lee/Grant has been severely penalized for having its gun in a casemate arrangement versus other vehicles.

I did point out that the gun did have a 14 degree traverse to either side after checking the FM on line.  This seems to be about in line with other assault guns of the time.  

The stats as given are OM1 -4 and OM2 -7 which seem like a bit too much of a handicap.  If I were going with the stats from similar vehicles such as the StuG III A-E, which had the short 75mm gun, I would think a -2 would be more appropriate.  The StuG III A-E has a -2 and -5 for OM1 and OM2.

It is always great to hear from you on the technical stuff and other things as well.


 

[Mark 1]

Hi Pete:

 

Good discussion. Pushing me to go back to the source material and check my own knowledge and understanding.  So back to the technical manual for crews of the Lee/Grant, in this case to: TM 9‑750 (Medium Tanks M3, M3A1, M3A2, 1942), I find that I was mistaken in asserting that the drivers were not trained to take input from the gunner. 

 

The TM states that when the gun reaches its traverse limit and the target is still out of view, the gunner signals the driver by patting his shoulder on the appropriate side, indicating the desired direction to turn the hull. The driver is expected to respond promptly, without direction from the TC in the turret.  The gunner's seat was actually more-or-less behind the driver's seat (and a bit to the right, facing forward as both would do), so the gunner should have been able to reach both shoulders without too much of a stretch.

 

We might also look into the training manual, which is FM 17-32 (Tank Crew Training).  But I don't recall there being much information there that was specific to the M3 Medium. It may have been from that manual that I got my impression that drivers weren't trained to change direction based on gunner inputs.  But I have not dug in to that one again at this point.

 

I can only imagine how quirky this must have made the tanks in a firing line. I don't know specifically about the M3, but the M4 Sherman had to go forward or backwards several feet to make a reasonable change in the direction the tank was facing. It did not pivot off of a stationary track, but moved on both tracks with one moving slower than the other.  I have never driven a Sherman (much less a Lee/Grant), but this issue is described quite explicitly in first-hand crew descriptions of how the Sherman did (or did not) manage to maneuver in tight spaces, such as at right-angle intersections in cities.

 

Because of this, I would expect that the M3 was less accurate (and slower onto the target) than other platforms when firing the hull gun from a short halt, and when firing at a moving target that was traversing across it's field of view. There was an additional factor affecting accuracy, though. In most M3s the gunner was provided only with a periscope for aiming. The linkage from gun to periscope was rather notoriously poor, with a fair bit of loose play. This was a matter in both the M3s and the early production M4s. This did in fact affect accuracy. After field feedback, the upgrade program for M4 Shermans included a direct-vision telescope for the gunner which was added when/as the widened gun mantlet was installed. M3s made after 1942 would also have a direct-vision telescope provided for the hull gunner. I don't know if this was also installed as a field upgrade (as on the Sherman) or not.

 

Given these two limitations, I think some penalties to OM-1 (stationary firing) and OM-2 (for firing from short halt) are appropriate. Are  -4 and  -7 the right numbers?  I don't really know.  Seems like a pretty stiff penalty to me, but having a TC distracted by giving targets to two gunners firing two guns, and having a gunner who has a technically accurate gun (US Army Ordnance designed guns that had notably lower dispersion than most other armies) attached to a sloppy sight should cost something. -4 or -3?  I could accept either.

 

I suppose it will be important to me some day. But for now, my M3s await the opportunity to get onto a game table. 

 

-Mark

(aka: Mk 1)

[Peter M. Skaar]

Hi Mark

I always appreciate your insights on this and in many other technical areas where I might have a gut feeling but you provide the hard data.

I think with the Grant, I will go with -3 for OM1 based on the not so good sight plus the TC having to do multiple duties at once and -6 for OM2.  This is one better for both (for the guys with the M3 Lee/Grants} than the original stats which I thought were a bit severe.  The M3 was the queen of the desert for a few months in the summer of '42 until the arrival of the Sherman. It is still not easy to hit with this tank but better and the AP can deal with almost any German tank of the time except for the Tiger I.

I have not really done much revision to the stats as given in the Data books and always appreciate what other might think before I change things.

[Mark 1]

I have been contemplating something said earlier in this thread, and wondering if I should raise it.  After noodling it for a while I decided I should drop it in the thread.

Pete:  I think I have a justification for your "gut feel" upgrade to the accuracy of the M3 Lee/Grant's 75mm gun.

 

Earlier in the thread, fan favorite Bob Benge said:

With that in mind, I think you will notice that there is a significant differences between the Grant and Sherman gun systems. Example: Grant has no gun stabilization and manual limited traverse (approx. 15 degrees to eash side of center) and the Sherman has Y-axis stabilization and hydraulic or electric/manual turret traverse. and whil I can see the arguement that crews turned off the stabilization I will provide this...

 

"Interestingly, while the technology was there, many crews didn’t use it effectively due to limited training or maintenance issues. Some even disabled it altogether. But for those who did use it properly, it offered a real edge in mobile engagements."

 

So ...

 

The M3 Lee most certainly DID have a Y-axis stabilizer for the M2 75mm gun. And as I know Bob loves him some evidence, I offer two illustrations from the Technical Manual for the tank (as named in the thread above):


Page 124 has a nice image of the wiring to the stabilizer.

 

And page 126 gives us a nice high-level schematic of the stabilizer mechanism itself.

 

I can not say with any confidence whether the M3 Grant provided to the British included this. IIRC The Chieftain may have made some comment on that topic. But I don't do Brits, so I have not stored that little tidbit in my soft squishy files.  But the M3 Lee, in US Army service, most certainly did.

 

And so, I think there is every justification for improving the OM numbers on the M2 75mm gun (and the M3 75mm gun, which was present in later production M3 Lees).

 

-Mark
(aka: Mk 1)

[Kenny Noe]

All,

 

I've been utilizing Large language Models (LLMs) for Generative AI testing and implementation/integrating into work structures.  I ran the question on the 75mm M2 gun on the Lee/Grant Tank platform and it came up with some interesting insights.

 

Understand LLMs and their application is still an evolving tech and I'm not postulating that it's to be 100% factually trusted.  There are documented risks that LLMs "hallucinate" (give odd  - off the wall - wrong answers) when not provided focused and specific questions.  But the replies on this subject were intriguing and I thought you'd be interested.

 

So read and "believe" what you will.  I thought this might open up more insight into this subject, but YMMV.

 

{Not looking to start discussions on AI or computer tech.  ODGW reserves the right to delete all non 75mm Gun stabilization comments w/o waring.}

 

**************************************************************************************************************************************

Did the 75mm M2 gun on the Lee/Grant Tank have stabilization? If so when was it installed? Was it effective?

 

 

Yes, the 75 mm M2 gun on the M3 Lee/Grant medium tank did have a stabilizer, but there are some important caveats.

 

1. Introduction of the stabilizer

The stabilizer was a vertical-axis gyrostabilizer, developed by the Westinghouse Electric Company.  It was fitted from the start of M3 production in 1941, including the M2 gun versions, because the U.S. Ordnance Department had mandated stabilization in all new medium tanks starting in 1940.  When the M3 switched from the 75 mm M2 (shorter barrel) to the M3 gun (longer barrel), the same stabilizer concept was retained.

 

2. How it worked

The system stabilized the elevation of the gun (not traverse).  It used a gyroscope to keep the gun steady relative to the horizon while the tank was moving.  The idea was to allow faster target re-acquisition after halts and to permit some level of firing “on the move” (though not with the accuracy of modern stabilizers).

 

3. Effectiveness in practice

Technically functional, but crews often left it turned off.

 

Issues included:

Required frequent calibration and maintenance.

Needed well-trained crews to use effectively.

Could not fully compensate for rough terrain; it reduced, but did not eliminate, gun movement.

In U.S. and British evaluations, it improved first-shot hit probability when moving slowly over smooth ground — but in combat, firing on the move was still rare.  Many British crews in North Africa called it “more trouble than it’s worth” and disabled it to avoid maintenance distractions.

 

4. Summary

Installed: From the start of M3 Lee/Grant production in 1941.

Type: Single-plane (vertical axis) gyrostabilizer.

Effectiveness: Marginal in combat, better in training or controlled conditions, often unused by crews.

 

If you want, I can also give you a side-by-side comparison of the M3 Lee’s stabilizer vs. the one used later in the Sherman, since they were closely related but not identical.

 

 

 

 

Yes, please compare

 

Alright - here’s a side-by-side comparison of the stabilizers used on the M3 Lee/Grant and the later M4 Sherman.

 

 

Bottom Line

Both systems were single-plane stabilizers — they only kept the gun steady in elevation, so the gunner still had to manually track the target left/right.  The M4’s stabilizer was evolutionary, not revolutionary — still not good for true “fire on the move” like modern tanks.  The main improvement in the Sherman’s version was smoother hydraulic response and slightly more rugged components, making it more dependable in dust and heat.  In real WWII combat, both were most useful for:

• Reducing aiming time after a stop.
• Keeping the gun roughly on target when moving between short halts.
• Not for sustained firing while moving cross-country.

 

If you want, I can also dig into wartime gunnery test results comparing M3 and Sherman stabilizers so we can put numbers on the hit probability difference — they’re surprisingly revealing.

 

 

 

 

 

yes display the gunnery test results

 

Got it - Wartime gunnery test results comparing the M3 Lee/Grant’s early Westinghouse vertical-plane stabilizer with the improved stabilizer in the M4 Sherman.

These figures come from U.S. Army Ordnance Dept. and British AFV Gunnery School trials between 1942–1943.

 

 

US & British Firing Trials — Stabilizer Performance

(All tests used the 75 mm M3 gun firing M72 AP or M48 HE at ~1,000 yards against a stationary target)

 

 

Key Observations

Training mattered more than the hardware — crews who practiced with the stabilizer could hit roughly twice as often at low speed compared to untrained crews who left it off.  Terrain was the biggest limiter — on rough ground, vibration and jolts exceeded what the single-axis stabilizer could correct.  British crews in North Africa often disabled the stabilizer early on because:

• It required daily calibration.
• Gyro drift could cause the gun to wander.
• Dust and heat reduced reliability.
• US doctrine by late 1943 encouraged stabilizer use for closing fire (while moving toward the target) but not for long-range precision fire.

 

Bottom Line

The M4’s improved stabilizer did provide a real advantage over the M3’s early unit — roughly +10% to +15% hit probability in tests under controlled conditions.  In real combat, the advantage was smaller unless the crew was both trained and disciplined about keeping it maintained.

[Mark 1]

It is helpful to ask your GenAI bot for sources when digging in on questions such as this.

 

I use GenAI to help me research and write often enough in my work. Depending on which engine, it really does "hallucinate" often. It is programmed to give you an answer based on probabilities of what comes next depending on its lake of data. If you ask it for sources it will often (again, depending on the AI engine) say "Good question. In this case we have estimated .... " or "in this case we are providing conclusions and summaries based on (this or that)".  In other cases it will give you specific sources.

 

There are two reasons I suggest this.  First, it helps you determine the reliability of the answer, and so can help in your learning.  Second, I WANT TO KNOW WHAT GUNNERY TESTS THESE WERE! I mean, yes please, I'd love to know about more gunnery test results on the Sherman (and the Lee - I don't have any reports from gunnery tests on the Lee).  

 

-Mark
(aka: Mk 1)

[Bob Benge]

Wow! Great conversation going on here. Enough to warrant a relook at the Lee/Grant OM123. Taking into account the info offered here I have run a recalculation of the Lee/Grant tanks and the M2/M3 75mm gun OM123. Using the stats that follow, here are the official updates:

 

Lee/Grant with M2 Gun

• Stabilization:      Y-Axis
• Turret Traverse: Manual Traverse (Hand Crank)
• Fire Control:       Basic Sighting (Periscope)
• Rate of Fire:       20 rds/min.
• Barrel Length:    31 caliber
• OM1 = -1, OM2 = -7, OM3 = no

 

Lee/Grant with M3 Gun

• Stabilization:      Y-Axis
• Turret Traverse: Manual Traverse (Hand Crank)
• Fire Control:       Basic Sighting (Periscope)
• Rate of Fire:       20 rds/min.
• Barrel Length:    40 caliber
• OM1 = 0, OM2 = -6, OM3 = no

 

I have updated all of the files and the the online download file of the WW2 Data Book with these updates.

 

This is great conversation! Thank youi very much and keep it going!