The Anemic? Katyusha

[John Kettler]

JasonC,

Thanks for the revised shell equivalence numbers.

Grisha,

The only way to effectively use the Katyusha in-game against moving armor is to use TRPs. Based on limited tests, even then it's still a bit iffy. In the real world, the best targets would seem to be assembly areas. Pictures of them I've seen look like they're full of densely packed targets.

Andreas,

Would it be possible for you to run a test to determine whether the in-game RS-132 is in fact close to the 152mm howitzer round in terms of performance (as JasonC says it should be), or if it instead falls more toward the 122mm howitzer or even the 76mm?

Regards,

John Kettler

[Andreas]

John

It would, but my cleaning lady has killed the power supply on my CM capable G4, so not until that has been fixed (can be a few weeks).

Or maybe, between that and the Der Kessel shutdown, Mars is trying to send me a message.

All the best

Andreas

[John Kettler]

Andreas,

Am not sure as to the nature of the cyberinjury inflicted by the cleaning lady, but am sorry it happened anyway. As to omens, chicken entrails are messy, so would suggest alternative approach used by ancients: roast a tortoise shell in a fire, then have a haruspex assess the cracks.

Regards,

John Kettler

[JasonC]

In game blast rating, the 132 rockets are much closer to the 152s. The M20 has the same blast (basically, within 2 points) as the 152mm gun-howitzer. The M13 is marginally lower (15% or so), but far above the 122mm gun, for example, and twice the blast of a 120mm mortar.

But their anti-armor characteristics are quite different. The rockets all come down in 12 seconds, while a 152mm gun-howitzer FO takes 4 minutes (and occasionally a little of the 5th) to all land. It is much harder to track moving armor for that long. They aren't going to stay on a TRP that long, either. An instant shoot also maximizes the chance of getting them unbuttoned and fragging the TCs.

But on the other hand, the sheaf of the rockets is vastly wider than the sheaf of the guns. If the guns are aimed even slight off they are going to simply miss, which won't happen to the rockets. But if they are aimed very close to a line a pair of tanks are along and directly between them, their chance of getting very near hits against those tanks is far higher than the chance of a very close rocket hit. Rockets, on the other hand, want a very large target, so their small direct hit chance is multiplied over the whole region. A single tank platoon is too small a target for them to be efficient - but is already larger than the densest part footprint of a 152mm firing with standard (close) sheaf.

Those are some of the reasons they aren't directly comparable. Here are some results I found testing them, though, in the course of which I noticed all of the above, in practice rather than theory.

I used as a target 5 Pz III Js late model, with 70mm fronts and 30mm sides but no skirts. Vanilla panzers, not Tiger thickness or lower BHE stuff. The 5 tanks were positioned 50m apart in a blob, 2 deep. The aim point was excellent, center of mass, and nearly on-line for the middle two. In some tests I had them buttoned, others not, to see frag effects.

I shot at them with 300mm rockets, 132mm M-13s, and 152mm gun-howitzers. Prep fire whole modules. I did not drive the tanks away from the impact area for the last, and let them button only when they buttoned, and unbutton if they decided to. I ran 5 tests of the 300 unbuttoned and 5 more buttoned, the same for the 132s. With the GHs I did 5 unbuttoned - other than fewer TCs I wouldn't expect much different buttoned for those, and it is relatively unrealistic for them anyway (no instant FP, targets just sitting there, etc).

The 300mm capped 10 TCs in 5 shoots when they were unbuttoned. The 132s got 5, and the 152s got 7. The 132s are clearly wasting a lot of frag firepower over a much wider area than the single tank platoon.

The 10 300mm shoots resulted in 3 gun damage and 6 immobilization results. The best had 2 while 3 of the 10 had none. The 10 132mm shoots got 1 full kill from a direct hit (top penetration, brewed up), 2 gun damage and 2 immobilization. Variance was high, with most not getting any, one getting the direct hit kill, and another accounting for 2 gun damage and an immobilization in a single shoot.

The 152 shoots were an interesting story. There were only 5 of these, and they got 6 full kills, none from direct hits, all misses so close the craters touched the vehicle or nearly so. 2 gun damage, no immobilization. The rear center tank was killed in 4 out of 5 shoots. Front center once and right side once. The two on the left side were never damaged and only once suffered even a crew casualty. The operative barrage footprint of the 152 battery for anti-tank purposes, was clearly much smaller than the platoon. It was more like a thin line 60m plus or minus along the axis and plus or minute 20m left to right. Being right in that zone had quite a high chance of KO and being outside of it had essentially none.

To replicate similar effectiveness with wide rocket strikes, you'd need a much larger target. 132s did get a full kill from a rare direct hit. And 300s were strong enough they inflicted damage of one sort or another reliably, though not all that much of it per shoot (1 average, 2 best). Rockets cap a fair number of TCs with their instant barrage effect, which would again be amplified by an appropriately larger target.

But to get full kills, 152mm and up tube arty are sufficient, if and only if the point of aim is nearly perfect. That is harder to achieve in real life than in these tests - platoons don't sit still for 4 minutes, they'd drive out from under a prep barrage after roughly half the module, and even TRP shots have to anticipate target position by one minute. But when the aim is just right, as few as 25 rounds of 152 can average a kill.

Otherwise put, the dense part of a dense sheaf 152 strike is dense indeed, compared to any rocket strike.

[John Kettler]

JasonC,

Thanks for running the test series and reporting the results in detail. This has been a most interesting and educational thread. Taking the accumulated evidence, it would appear that the in-game depiction of the BM-13 Katyusha's 132mm rocket is about right.

Further, while it clearly does have a substantial

charge to mass ratio (4.9:22), it isn't in quite the shattering realms of, say, the the U.S. M3 shell for the 4.2 inch mortar (8:22). Do you happen to know the charge to mass ratio for the 152mm howitzer shell? I doubt it's more than half that of the 132mm rocket.

I wish the in-game artillery modeling allowed for the sheaf to be perpendicular to gun-target line,

rather than parallelling it, since this makes it much harder to model defensive barrages through which advancing armor must drive. As it is, for 122mm and up, the ROF is so low that unless the armor's practically trapped by terrain and can't maneuver, the threat level is almost nil. This is for a single battery firing. I have yet to try a

battalion level shoot. Maybe that'll give me the wall of explosion effect I seek, especially if I use staggered TRPs.

I see from your profile you're a research analyst.

If you don't mind my asking, what kind and for whom?

Regards,

John Kettler

[JasonC]

I work for a software company. We make tools for scientists. So we have to know all their formal methods, and then we want to help extend them.