Tank Gun Damage Expectations?

[c3k]

Gents,

I'd like to get a bit of educated dialogue going. Here's my question:

"Do you think the damage modeling for tank main guns is correct? What supports your position?"

The "why" is MORE important than the "yes" or "no". Extra credit for using real sources.

Thanks,

Ken

[MikeyD]

Tank guns aren't made from armor steel but steel optimized for barrel manufacture. A lucky hit is liable to take a gauge out of it, bend the barrel, and for German tanks bend the blast deflector so its blocking the tube. There was a famous photo from the 1980s of a T62 gun barrel that had been completely penetrated at a highly oblique angle by an Israeli 105mm APDS(?) round. It was a spectacular shot. I just did a quick google search but couldn't locate the photo on the web.

[c3k]

So a how much of a hit should render a barrel inop?

Assume a side-on shot: does the diameter of the barrel matter for resistance? (E.g., is a 128mm barrel immune to damage from 20mm @ 1,000m/s, but a 75mm barrel would be rendered inop?)

Does the impact area, as a fraction of the incoming round matter? E.g., does a 75mm shell need to impact at least 25mm of the barrel?

(There's a picture somewhere on my shelves attributed to a German recce unit which holed the barrel of a KVI to put it out of action.)

Ken

[SlowMotion]

I'm surprised of how often the gun is damaged compared to whole tank being destoyed. No real reason - the gun just seems such a small part of the whole tank area that can get hit.

[YankeeDog]

So a how much of a hit should render a barrel inop?

Assume a side-on shot: does the diameter of the barrel matter for resistance? (E.g., is a 128mm barrel immune to damage from 20mm @ 1,000m/s, but a 75mm barrel would be rendered inop?)

Does the impact area, as a fraction of the incoming round matter? E.g., does a 75mm shell need to impact at least 25mm of the barrel?

(There's a picture somewhere on my shelves attributed to a German recce unit which holed the barrel of a KVI to put it out of action.)

Ken

It would be a b*tch to confirm, as I don't recall exactly where I read it, but ISTR finding some German damage reports from the East Front showing that 14.5mm ATR hits could render the 75mm guns on the PzIV/lang inoperable by "dimpling" the barrel -- that is, fairly flat hits on the outer surface of the barrel would cause enough deformation to compromise the shape of the gun tube, making it dangerous and/or impossible to fire the main gun.

If my recollection is correct, apparently it doesn't take a particularly large/energetic projectile to damage a typical WWII tank gun barrel, *if* the hit on the barrel is at a relatively flat angle (which, granted, would be pretty hard to achieve in most circumstances).

[JonS]

"Do you think the damage modeling for tank main guns is correct? What supports your position?"

There's nothing special, I think, about tank guns, so depending on why you're asking it might be worth expanding your question to 'guns', or perhaps 'cannon', or 'ordnance over 20mm', or sumfink. If nothing else that would expand your sample size.

AFAIK, gun barrels are reasonably over-engineered ... like pretty much everything that gets painted green. There's also a number of different ways of building them up, so the specific manufacturing technique probably has some bearing on it's resistance to and tolerance of damage.

There's also the recoil and sighting system, of course, both of which are susceptible to damage. Neither require direct hits to be rendered U/S, the sighting system especially. While having the sights KO'd doesn't prevent the gun from fiing, it does prevent it from firing effectively.

[c3k]

JonS,

I'm ignoring guns other than tanks for several reasons:

- If they're too small, I don't care. (I'm sure rifles got shot up by enemy fire, but the man holding it would probably be wounded as well.)

- Towed guns are usually engaged with HE in an attempt to disable the soft crew.

Tanks are usually engaged with solid shot during this era. (Heat, etc, I know: "usually".) The GAME specifically models tank guns. It is a discrete system. Fire control and optics are separate systems. My understanding of the game's "fire control" damage model is that it represents the slewing and elevation system.

"Gun" seems to be the barrel and recoil mechanism.

[JonS]

Ok, so it isn't an abstract enquiry, it's specifically related to the game. That's important context.

You're correct about guns (towed guns) mostly being engaged by HE. But A-Tk guns were engaged by direct fire (often HE, but still ... direct) and splinter damage would have at least some of the charateristics of AP damage.

There's probably some engineering data around on the resistance of tubes to damage, and most likely a formula which relates diameter, thickness, size of impactor and force of impactor to expected damage. Maybe not even damage; the manufaturing processes of stamping and forming are basically the same mechanism as AP penetration. A confounder there would be the specific manufacturing techniques used to make the barrel - autofrettage, sleeves, liners, etc. - which would generally be a lot more sophisticated than for a steel pipe, and make working out the effects of a strike somewhat trickier.

But as already pointed out, working out the effects of a hit on the barrel pre-supposes a hit on the barrel. Deliberately acheiving a hit on a tank's barrel is a non-trivial task, one that was probably beyond the capabilities of aiming and sighting mechanisms of any WWII weapon system at reasonable ranges. (Which is not to say that barrel hits never happened. Clearly they did But deliberate, aimed, barrel hits? Eh ... not so much.)

[c3k]

...(Which is not to say that barrel hits never happened. Clearly they did But deliberate, aimed, barrel hits? Eh ... not so much.)

Several accounts of early Germans doing just that. Combat photos confirm. KV-2 was easy - relatively, that is. KV-1 was harder.

Very rare, but done successfully a few times.

My main line of enquiry is game related. How often does it occur, and does it "feel" right?

[MikeyD]

A lot of hits are on hull-down vehicles and much of target area on a hull down vehicle is the gun mantlet (depending on the vehicle). So it depends on how broadly you define 'gun damage' how common a hit might be. This reminds me of a debate back in CMBB days. People were claiming its better to have your PzIV fully-exposed than hull down. Their reasoning was a hull-down vehicle would only get turret hits and PzIV turret armor is just 50m. So exposing the full vehicle would increase the chance of hitting the 80mm thick bow instead.

[c3k]

I define "gun damage" by the game's mechanism. Is the gun damaged?

The game's tank UI is the determination if the gun is damaged.

[MG TOW]

Would this also refer the the gun hydraulic mechanisms as well. Maybe if the mantlet takes a solid hit this would damage the gun stabs, not just the barrel, also the optics as well which is another category, and give the gunner raccoon eyes.

[DasMorbo]

In real-world the gun is defined as the tube, breech and recoil mechanism. And it is the recoil mechanism which is the biggest and most vulnerable part, consisting of a high-pressure hydraulics system with a lot of gaskets, precision parts and so on.

I guess most of the hits rendering the gun inoperable in the game can be traced back to the recoil mechanism being shaken up, even by non penetrating hits, not actual gun barrel-hits.

Note: I always get itchy when my german tanks receive non-penetrating fire, because the inner workings of a tank are quite delicate (transmission, dirve shafts, optics, gun mechanism).

Just for the interested: the other parts of a tank gun are the fire control mechanism, consisting of the elevating mechanism (rotation is part of the turret system in normal tanks) and the electrical trigger that fires the gun. And of course the optics.

Credits

Where I got this from? From memory. I'm doing military scale-modelling for 20 years and do qiue some research for every model tank I build. So it should be correct but may contain some errors.

Cheers

Olf