"Does size matter?" Topic

No, not that!

I'm talking about target size when fired at by a tank or ATG. Does the size of the target matter, so far as the ability to hit it is concerned. Intuition says it should matter, at least as fairly close range, say 100 yards/meters. But at, say, 1,000 yards/meters does the difference between a VW and Tiger II matter? how about the difference between a Stuart and a Sherman? or between a Pz IV and a Panther?

Of course it does.

Considering dispersion only the 75mm has a 100% to-hit chance for the PZIV up to 400m and 87% at 1000m.
For the Tiger I it has a 100% chance up to 500m and 95% at 1000m.

It matters less at longer ranges. Normal engagement range is about 1000 meters. At 1500 meters, many weapons can still reliably hit their target. Much past that, it becomes a craps shoot.

At any ranges past 500 meters, I would think that the save of an AFV would matter very little. The size of a small vehicle (Jeep, Motorcycle) compared to an AFV might matter more.

I will have to correct myself a little. The following information was drawn from a Ballistic Research Laboratories Report (#590) entitled "The Range and Angular Distribution of A.P. Hits on Tanks" by R. H. Peterson, APG, December 1951. Taking information from both British and American reports in the Northern European theater, the author states that based on the range distributions the Average range of opening combat for tanks was 660 yards. A bit more than I first stated. However, he stated the following "It is to be noted that the range at which the most encounters took place was 300 yards or 1/2 the average range." Noting the graph accompanying part of the report – "For example, from the graph 67% of all engagements were at ranges greater than 200 yards and 65% were at ranges greater than 400 yards. Hence 22% or about 1/5 of all engagements were at ranges between 200 and 400 yards. Only 2% of all engagements were at ranges greater than 2000 yards."

Of course the size of the target matters.

An infinitely large target, all shots would hit. An infinitesimally tiny target, all shots would miss unless they passed within half a shot calibre. In between these extremes is the domain of real P(hit), and it depends on the relation between projectile dispersion and apparent target size (accounting for range).

Assuming that projectile dispersion is normally distributed, target size will matter less at longer ranges to the extent that the fat parts of the Gaussian distribution no longer fit within the subtense of the target. But target size still matters, even if only quasi-linearly.

All the best,

John.

An example of wartime accuracy …

In September of 1944, the British Army conducted firing tests with 2 17pdr-armed Sherman Firefly tanks. The tests were conducted using standard range targets which, for the British Army gunnery at that time were 6' by 6'. The results and comments were published in War Office Reports WO 291/1263 and WO 165/135 dated 22 September:

400 yds
APC hit 90.5%
APDS hit 56.6%

600 yds
APC hit 73.0%
APDS hit 34.2%

800 yds
APC hit 57.3%
APDS hit 21.9%

1000 yds
APC hit 45.3%
APDS hit 14.9%

1500 yds
APC hit 25.4%
APDS hit 7.1%

The same WO reports include these comments as guidelines for aiming:

"… useful range of APC ammunition was 900 yards while that of APDS was only 450 yards."

"… there is no use in attempting to pin-point vital zones in targets at ranges over about 200-300 yards."

Note that these tests were conducted under range conditions. No stresses of combat -- no one shooting back, no mortal risk, no accumulated fatigue. The distances to the target were precisely known, and there was infinite time for aiming.

Given the results the War Office recommended that it was not useful to try to hit specific parts of a target tank at over 200-300 yards. Don't aim for the weak spot … you won't be able to hit it. Better to aim for the center of mass, to improve your overall chances of hitting the target at all.

Any gun hits somewhere in a radius around the point of aim. This radius is referred to as the gun's dispersion. ~90% hits at 400 yards indicates that the radius with APC, at that range, is somewhat greater than 3 feet. ~50% hits at 400 yards indicates that the radius with APDS is about 6 feet.

At 1000 yards the APC radius is somewhat more than 6 feet. So a target that is smaller than 6 feet in each direction from the point of aim -- ie: 12 foot tall and 12 foot wide -- is unlikely to be hit except by luck. The APDS radius is closer to 24 feet. So you are unlikely to hit a target that is less than 48 feet tall and wide.

Size matters.

I have seen no information indicating the firing age of the guns used, so can not say if they had worn barrels. But what you see in these results is a very high dispersion. You should not believe this is typical of guns at that time. US Army Ordnance would never have accepted a gun for service with this level of dispersion. But British AT guns, in particular the 17pdr, were optimized for high velocity rather than for low dispersion.

Dispersion is only one component of accuracy. In combat, beyond about 750 yards, range estimation (and ranging errors) can be even more important. Mis-estimate the range at 1000 yards by 200 yards, and you could easily be shooting 15 feet over or under your point of aim. Higher velocity guns (like the 17pdr) were less prone to ranging errors (because their projectiles flew in a flatter trajectory), and so emphasizing velocity was not necessarily a bad idea.

But in all cases size matter.

-Mark
(aka: Mk 1)

Er, Mark….
WO 291/1263, Firing Trials, 17pdr Sherman
"Table VI has been constructed which shows the probability of a hit on a target 5' wide by 2' high
(representing a Panther turret) at various ranges using both types of round."

I can't say these tests were consistent.

WO 291/180, Accuracy of anti-tank gunnery
Ranges in yards, target assumed to be Pz VI size.
Probability (%) of hitting static hull-up target with first round:
for… 500yd
17 pdr line 100%
range 98%
both (hit) 98%

for…1000yd
17 pdr line 100%
range 46%
both (hit) 46%

WO 291/1263, Firing Trials, 17pdr Sherman
"Table VI has been constructed which shows the probability of a hit on a target 5' wide by 2' high
(representing a Panther turret) ….

WO 291/180, Accuracy of anti-tank gunnery
Ranges in yards, target assumed to be Pz VI size ….

Ah, Mobius my friend, your information seems to disagree with mine.

I will gladly bow to your superior research. Could you share with me the source materials? I have only second-hand (re-published) fragmentary contents of these W/O reports. Do you have originals? Or at least more complete or reliable fragments?

-Mark
(aka: Mk 1)

As above, of course target size matters from the pov of hit probability. If it didn't there wouldn't be much point in going hull down would here?

Or lying down, if one is an infantryman.

Even with the best range estimation in the world, rounds impact around a mean and the size of that grouping gets bigger at longer ranges. so arguably target size matter more as things get further away.

When considering AP fire, it is also far less able to penetrate as well, making the cumulative effects for long range AT fire fairly disastrous.

Whizzo super guns aimed with high quality optics and range finders such as those found in Nashorns and Jagdpanthers being exceptions of course. But many Jagdpanthers seemed to end up being used as ersatz Panthers stuck in the middle of the Reichswald or anonymous East Prussian forests, which rather negated those advantages.

I will gladly bow to your superior research. Could you share with me the source materials? I have only second-hand (re-published) fragmentary contents of these W/O reports. Do you have originals? Or at least more complete or reliable fragments?

I have to bow to John Salt who collected and transcribed all the WO reports that I saved.

I just put them on my site. I hope John doesn't mind.

link

link

Drilling down to a better comparison of a 2'x5' target to a Pz IV turret target. Data from WO 291/1263 is not that far off WO 291/180.

Ranges in yards, target assumed to be Pz VI size.
Probability (%) of hitting static hull-down target after first round:
Gun…….500….1000
17 pdr…..88%…..51%

46% vs 51% is pretty close.

It matters less at longer ranges.

That was my assumption, yes. At some point the target, even a Tiger II, looks like just a speck or spot on the landscape and even the tiniest percentage of a degree off target will be a miss.

of course target size matters from the pov of hit probability. If it didn't there wouldn't be much point in going hull down would here?

Well, it still means they can't hit the hull, doesn't it? No matter how often they can hit the turret.

Normal engagement range is about 1000 meters.

I have read that in NW Europe it was rare to be able to see a target at more than 500 yards/meters.

Mis-estimate the range at 1000 yards by 200 yards, and you could easily be shooting 15 feet over or under your point of aim.

Therefore the height of the target would be more important than its width.

> I have read that in NW Europe it was rare to be able to see a target at more than 500 yards/meters.

That is due to not having site lines, not due to optics as such. In the Russian steppes longer ranges were quite possible.

> Well, it still means they can't hit the hull, doesn't it? No matter how often they can hit the turret.

But if it were JUST as easy to hit the turret as it was the hull AND turret there would be no point in going hull down, smaller targets are harder to hit at all ranges is the point. Even tanks with thinner turret armor then hull armor go hull down in order to make their target size as small as possible.

> Therefore the height of the target would be more important than its width.

That is true, usually getting the shot lined up is the easier thing to do while getting the range lined up so the shot falls on the target without overshooting is the harder bit – at least where down the barel aiming is not possible due to distance.

Looks like the heavies have beat me to this topic…

Target size does matter. Eventually, the shot dispersion will match the size of the target, so there is a chance that you could aim correctly and still miss.

But range estimation error is a far greater factor than the innate weapons dispersion. Heck, WIND estimation error is a greater factor than the innate dispersion of the weapon.

Unless the vehicle has some kind of stereo-optical (or laser, if you're playing moderns) rangefinder, crew skill matters more than what gun they're shooting!

> I have read that in NW Europe it was rare to be able to see a target at more than 500 yards/meters.

That is due to not having site lines, not due to optics as such.

I would have said that, but I thought it was obvious. Sights that were good on other fronts didn't suddenly fog up in NW Europe. It was the prevalence of hills, trees and buildings that blocked LOS. I did read of one US TD that took out panzers in the Ardennes at 1000 yards as they came over a hill, firing right down a road.

Obviously, at longer ranges at least, height of the target is the main consideration. But at closer ranges (say 500 yards/meters or less) with high velocity guns, is the trajectory flat enough not to have to worry about estimating the range?

I guess what I'm really asking is: HOW MUCH size difference matters, or should make a difference in my rules. Is it significantly easier to hit a Panther than a Pz IV? a Sheman than a Stuart?

Still looking for answers here.