WWII - sp. ATguns/TDs VS. tanks (in an infantry support role)

[Kaunitz]

My recent H2H game taught me the differences between self-propelled ATguns (or tank-destroyers) and proper tanks in an infantry support role the hard way. I thought it would be interesting to discuss the topic and share some experiences here. If possible, though, I'd like to keep the discussion based on gameplay, not on real doctrines. I'm not really an expert, when it comes to definitions. For easyness' sake (disregarding that the two types discussed here were probably more differentiated based on their tactical and operational deployment rather than by technical intricacies?), let's just say that: 

• A tank has a turret and at least 1 MG (more often 1 turret and one hull MG). Most tanks in CM have ample supply of both, HE and AP ammo. In CM, it's usually much more expensive than a sp. ATgun
• A sp. ATgun has no turret (and the traversable angle of the gun is often very limited) and no MG. Most sp. ATguns in CM are focused on AP ammo and carry only few HE rounds (with some exceptions, e.g. SU 76M). An ATgun is usually much cheaper than a tank.

Now a few thoughts:

• In an assault, you often want to lay down fire on several positions within a single turn at slightly varying angles to your vehicle's front. Because of its turret, the tank is so much better at this. As the whole vehicle needs to point in the direction of the shot, a spATg would need to approach in a curved, snake-like line or, alternatively, stand still for long intervalls to turn on its tracks. Any errors in planning the movement can be fatal, as the spATg might not fire at all if you fail to give it enough time to turn (pay attention to the turning stat of your vehicle!!). The tank, by contrast, can go in a straight line and fire at any angle.  
• For the same reason, the tank is much superior to the spATg in what could be called "corner situations" - these are the typical situations in which you want to go in one direction, but fire in another direction. For example, take a crossroad in a village - you know there is an enemy position around the corner. The tank can rotate its turret while still in cover, then expose itself and fire almost immediately at 90°. The spATg would need to expose itself, then rotate slowly on its tracks, and only then could it fire. So, for any kind of close combat and corner situation, the tank is superior. 
• In many cases in CM, main guns - the only weapon spATguns have - are tricky to use. The main gun is more dependent on proper aiming (and on confirmed contacts, for that matter). If your target is positioned somewhere around the same height as your muzzle, you will run into troubles. The main gun's HE shells are effective only if they actually hit something - either the ground or an obstacle. If they miss, they often have no effect on the intended target whatsoever, depending on the lay of the land. E.g. if the opponent is behind a gentle ridge, almost at the same height as your muzzle, and the surroundings are flat, it can be very hard to get a valid area target anywhere close to the suspected contact. Shots aimed too low will do nothing as the target is in cover behind the ridge. Shots aimed too high will sail over the heads of the target harmlessly. Note that this problem is most notable on flat terrain with main guns that are located close to the ground (vehicles with low silhouettes) and therefore may affect spATguns more than tanks. Main guns in turrets are located "higher" and can therefore see over terrain much better and area-target spots more accurately/easily - on a flat surface, the target will be positioned lower than the gun, making it easier for the gun to hit somewhere close to it. Positioning yourself somewhere higher than your target (on a hill) can solve the problem, if you're lucky enough to find such an elevation on the map. NOTE: I wished that assault guns with low velocity/curved trajectory weapons would get some kind of bonus here. I really think they should be allowed to target reverse slope areas (like mortars).
• The MG, by contrast, is less dependent on actually hitting the target in order to be "effective". So this is a big plus for tanks. With a tank, you can try to get the turret-MG in a position where it can deliver grazing fire (bullets traveling close to the ground over flat terrain), which allows you to strafe areas (far beyond your MG's line of sight) that are hard to hit with your main gun. Tanks would be even better if the game allowed you to use their hull-MG for area-fire commands (unless hull-down, the hull MG, being closer to the ground level, can often achieve grazing fire more easily than the turret MG whose fire will be directed "downwards", hitting the ground instead of traveling on at dangerous grazing height). 

 

 

Edited October 20, 2018 by Kaunitz

[Michael Emrys]

10 minutes ago, Kaunitz said:

Shots aimed too high will sail over the heads of the target harmlessly.

If that is indeed the case, the practice strikes me as questionable. I believe that if I were a soldier lying on the ground trying to stay alive and maybe shoot some enemies, having HE shells flying close overhead would certainly impact my morale at least a little. I might not break and run immediately, but my resolve would certainly begin to weaken.

Michael

[nik mond]

The theory is tanks were suited for attack and breakthrough tactics, and tank destroyers were to counter the enemy armor spearheading such an attack. The shortcomings of such a doctrine is debatable but you still see tank destroyers today in different forms. There is also the allied tank destroyers with open turrets m10 m18, 36.

In CM TDs are definitely the underdog, doomed if facing the wrong way when tracked, and have vulnerabilities, all have more vulnerabilities to infantry. I take too many chances with TDs. Tank destroyers are not tanks, and assault guns are not tank destroyers. AGs like the Stuh42 have a slow fire rate and few heat rounds, definitely made for anti infantry.

[domfluff]

The British doctrine for Tank Destroyers (The M10 and the Achilles in Combat Mission) was for them to be used as mobile AT guns. They're not intended to support infantry, or hunt down armour, but to take up static positions and move from them quickly and somewhat protected - countering most of the issues that AT Guns have, at the cost of stealth.

You can see the appeal of that - being able to take up forward defensive positions, or get away from them when things get too hot, is tremendously attractive, and something which they're pretty well suited for.

Assault guns in general can be useful in the attack - if you are attacking a static position, then you don't necessarily need the flexibility of a tank - something like a Stug III is fine if you need it to go in a specific direction and lay down HE on a specific target. Assault guns also tend to be smaller than tanks for the same firepower (or rather, they remove the turret to up-gun the tank), so smaller, cheaper and lighter can all help, in certain circumstances.

[Bulletpoint]

6 hours ago, Kaunitz said:

If your target is positioned somewhere around the same height as your muzzle, you will run into troubles. The main gun's HE shells are effective only if they actually hit something - either the ground or an obstacle. If they miss, they often have no effect on the intended target whatsoever, depending on the lay of the land. E.g. if the opponent is behind a gentle ridge, almost at the same height as your muzzle, and the surroundings are flat, it can be very hard to get a valid area target anywhere close to the suspected contact. Shots aimed too low will do nothing as the target is in cover behind the ridge. Shots aimed too high will sail over the heads of the target harmlessly. Note that this problem is most notable on flat terrain with main guns that are located close to the ground (vehicles with low silhouettes) and therefore may affect spATguns more than tanks. Main guns in turrets are located "higher" and can therefore see over terrain much better and area-target spots more accurately/easily - on a flat surface, the target will be positioned lower than the gun, making it easier for the gun to hit somewhere close to it. Positioning yourself somewhere higher than your target (on a hill) can solve the problem, if you're lucky enough to find such an elevation on the map.

Not sure if you're right about this. Both proper tanks and self propelled guns have difficulties (spotting and) hitting a target behind a ridge - that's why the hull down tactic was invented.

You're saying a real tank has less trouble with this, because it's taller and the gun is higher off the ground. But most often, the tank would also try to go hull down, so its gun would also close to the ground with respect to the target, making it equal to the SPG.

Also, even if it fires from its full height, the angle of shot is nearly the same. After all, it gains only about a half metre in height, but the target might be 500m away.

So you're drawing a triangle ABC where:

StuG A=1.55 metres (gun height), while B (distance to target) is 500 metres. Angle to ground: 0.18 degrees

PZ IV A= 1.95m, Distance 500m. Angle to ground 0.22 degrees.

So, the difference in angles would be 0.04 degrees, just four percent of one single degree.

 

Sources:

Data on tanks:

http://www.wardrawings.be/WW2/Files/1-Vehicles/Axis/1-Germany/02-mPanzers/PzKpfw4/Data/PzKpfw-4H.htm

http://www.wardrawings.be/WW2/Files/1-Vehicles/Axis/1-Germany/05-Sturmpanzers/StuG3/Data/StuG-3G.htm

Online triangle calculator for those of us who forgot everything about maths after highschool:

http://cossincalc.com/#angle_a=&side_a=1.95&angle_b=&side_b=500&angle_c=90&side_c=&angle_unit=degree

 

Edited October 20, 2018 by Bulletpoint

[Kaunitz]

@ Bulletpoint

Just a short note, as I'm in a hurry. You're right on the angles. Some calculations:

angle of impact on the ground (perfectly flat surface):

muzzle height = 1.5m

• @50m --> 1.718°
• @100m --> 0.865°
• @500m --> 0.173°
• @1000m --> 0.0859°

muzzle height = 2m

• @50m --> 2.291°
• @100m -->1.146°
• @500m --> 0.229°
• @1000m --> 0.115°

Effect of inaccuracy. Suppose that inaccuracy adds +/- 0.1 degree:

firing at target at 500m:

• muzzle height 1.5m: 
  • short (+0.1°) --> hits 186m
  • long (-0.1°) --> hits 1177m
• muzzle height 2m:
  • short --> hits 348m
  • long --> hits 888m

firing at target at 100m

• muzzle height 1.5m: 
  • short (+0.1°) --> hits 89m
  • long (-0.1°) --> hits 112m
• muzzle height 2m:
  • short --> hits 91m
  • long --> hits 109m

 

So you're correct that the difference in accuracy caused by the differences in muzzle height are probably not that big, or, more specifically, that a muzzle with higher elevation is not significantly more accurate (it will still hit closer to the target, but not close enough as even minor deviations lead to shots going far off the mark at those flat angles...).

And overall, these calculations also show that even slight deviations from the perfect gun-elevation will make the shells over- or undershoot by a lot. That's why I say that generally speaking, main guns have a hard time to hit flat target (no houses, trees) s if they're on the same height level. Firing upwards or downwards on a target, by contrast, gives guns more wiggle-room.

My feeling might be much more related to being allowed to area fire on = seeing the ground of squares. Here the higher elevation might matter indeed as your LOS will travel on above the level of most micro-terrain for longer distances. 

 

PS: All calculations were based on the assumption that main guns (unlike small arms) on "area fire" target the ground, not a point slightly above ground level.

Edited October 21, 2018 by Kaunitz

[Bulletpoint]

4 hours ago, Kaunitz said:

My feeling might be much more related to being allowed to area fire on = seeing the ground of squares. Here the higher elevation might matter indeed as your LOS will travel on above the level of most micro-terrain for longer distances. 

Higher elevation as in being on a hill or in a church tower - definitely. Being in a tank turret half a metre higher up, not much. That's why even tanks need to get extremely close before they can area fire in a field of crops.

Now put away your calculator and play the game. It's your turn

Edited October 21, 2018 by Bulletpoint

[JoMac]

4 hours ago, Kaunitz said:

@ Bulletpoint

Just a short note, as I'm in a hurry. You're right on the angles. Some calculations:

angle of impact on the ground (perfectly flat surface):

muzzle height = 1.5m

• @50m --> 1.718°
• @100m --> 0.865°
• @500m --> 0.173°
• @1000m --> 0.0859°

muzzle height = 2m

• @50m --> 2.291°
• @100m -->1.146°
• @500m --> 0.229°
• @1000m --> 0.115°

Effect of inaccuracy. Suppose that inaccuracy adds +/- 0.1 degree:

firing at target at 500m:

• muzzle height 1.5m: 
  • short (+0.1°) --> hits 186m
  • long (-0.1°) --> hits 1177m
• muzzle height 2m:
  • short --> hits 348m
  • long --> hits 888m

firing at target at 100m

• muzzle height 1.5m: 
  • short (+0.1°) --> hits 89m
  • long (-0.1°) --> hits 112m
• muzzle height 2m:
  • short --> hits 91m
  • long --> hits 109m

 

So you're correct that the difference in accuracy caused by the differences in muzzle height are probably not that big, or, more specifically, that a muzzle with higher elevation is not significantly more accurate (it will still hit closer to the target, but not close enough as even minor deviations lead to shots going far off the mark at those flat angles...).

And overall, these calculations also show that even slight deviations from the perfect gun-elevation will make the shells over- or undershoot by a lot. That's why I say that generally speaking, main guns have a hard time to hit flat target (no houses, trees) s if they're on the same height level. Firing upwards or downwards on a target, by contrast, gives guns more wiggle-room.

My feeling might be much more related to being allowed to area fire on = seeing the ground of squares. Here the higher elevation might matter indeed as your LOS will travel on above the level of most micro-terrain for longer distances. 

 

PS: All calculations were based on the assumption that main guns (unlike small arms) on "area fire" target the ground, not a point slightly above ground level.

On the same Token, you have the lower velocity guns (M4/75 Sherman), and light Field Pieces that will have a lesser chance of sailing over the target, and will hit closer to it (at least on consecutive shots). 

Edited October 21, 2018 by JoMc67