On Sun, Jul 12, 2020 at 2:38 PM Ethan McKinney <xxxxxx@gmail.com> wrote:

On Sun, Jul 12, 2020 at 1:44 AM <xxxxxx@gmail.com> wrote:

On Sun, Jul 12, 2020 at 1:03 AM Ethan McKinney <xxxxxx@gmail.com> wrote:
No, the question is about muzzle velocity, not size. Given a constant bore (3cm, 7.5cm, 10cm, etc.), higher velocity will somewhat decrease the effectiveness of the HEAT ammunition.

So are the 'Medium' and 'Large' gun types not bore related in Striker?
Where are you getting "Medium" and "Large"? As I indicated, I think that you misread "Medium Velocity" as medium-sized and then mentally substituted "Large" for "High Velocity." Maybe I missed something?

That appears to be part of the issue. So we have differing cannon velocities - from mortar/low-vel through med-vel, high-vel, and hypervel (in two flavours). Noted.

Keep in mind that HEAT is a shaped-charge warhead.

I know that, though I always had assumed the 'superplastic jet' was from the armour of the vehicle but it is actually from an internal iron or copper cap.
Not a cap, but a liner. That's the difference between convex and concave. https://www.lonesentry.com/articles/ttt08/pics/armor-piercing-projectiles.jpg

Not that the "jet" is actually solid (not molten) copper. There's a lot of nonsense out there about "molten copper" jets and even "plasma jets." Experiments firing sectioned shaped charge warheads into water tanks show conclusively that the jet is not molten. You can also do back of the envelope energy calculations that show that it just can't melt the liner. That's with ridiculously optimistic assumptions. All of this is why I vastly prefer the term "trumpet": it doesn't cause the conceptual confusion of "jet."

It sounds to me then like what it really describes the the plastic deformation of a solid into a new shape that is directed into a very particular shape (a penetrator) without anything being in a liquid state. Does that capture it?

I don't think anyone's using iron in HEAT warheads because it's just not efficient.

Early ones used iron and tin apparently. Nobody is anymore.

I thought your comparison with the 76mm was against the prior 75mm gun the Americans used. So it wasn't quite a 'same bore' issue, but you get a bigger bore (ever so slightly) and a higher muzzle velocity and that leads to reduced explosive payload...

The 76mm gun had a much longer barrel and the rounds had more propellant, giving them a much higher velocity. The 1mm difference was irrelevant to performance.

So, the gun was a higher velocity and that changes the performance, but reduces the efficacy of the HEAT round then? (vs the lower velocity 75mm?) Or were both the 75 and 76 limited in about the same way for how much HE you could pack in and thus HEAT performance might have differed much between the two guns?

Or was the 76 capable of firing further but with a less effective HEAT warhead?

Here's the dramatic comparison of the Sherman with 75mm, 76mm, and 105mm guns: https://qph.fs.quoracdn.net/main-qimg-aa83244794fe858fbfdfd0c362a54450

Kinda fuzzy, but the middle one has a much longer barrel.

Let me ask the obvious question: If my normal HE was compared to the same 76mm's HEAP/HEAT, should I note expect it to have better penetration than the HE? (I mean, why else would they develop it and call it high explosive anti-tank...)

Yes, but I'm not sure what you're asking. HEAT is completely different from HE in its operation.

What did they have before HEAT? I assume HE is the basis of slow velocity guns (forex: assault guns or artillery). Then along came HEAT. My point is if it is supposed to outperform whatever came before (I just sort of assumed it was some HE but it may have been something else), one would think even in medium velocity guns it would have to outperform what was there before, not so?

HE is for use against infantry, mild fortifications, etc. It's not intended for use against tanks, although WWI tanks had such thin armor that direct hits from 75mm and larger guns could typically penetrate it even with HE rounds. Later, HE was sometimes used in extremis with the fuze removed, so that the metal parts would be inefficiently driven against the armor. Extremely large guns, like the 152mm on the JS-152, could do significant damage simply through blast (a 100 lb. shell from a medium-velocity gun is no joke).

Yes, a howitzer round is still unpleasant...

Let me rephrase the question as I still don't quite get the answer I'm looking for here...

If the 75mm sherman had a non-HEAT anti-armour round and a HEAT one and so did the 76mm sherman, was the ratio of efficacy versus armour the same (HEAT vs. other round type) in both generations or variants of the Sherman?

HEAT is entirely unrelated.

SFP isn't used in gun rounds because it has no advantages over HEAT. They also have lower penetrations than HEAT warheads of the same diameter.

Interesting.

However, HEAT rounds have a pretty narrow range of stand-off distances for effective penetration. Moving away from the optimal stand-off distance rapidly reduces penetration.

Yes, but I thought some of the multi-charge versions were a bit more capable. Of course, some of them might be in missiles vs. guns - I don't know.
Multi-charge is only possible in missiles so far. In any case, the purpose is that the smaller forward warhead detonates Explosive Reactive Armor (ERA) and the primary warhead penetrates the actual metal armor.

The three charge version mentioned handles the ERA and a couple more layers. I assume that's rather large though and the development must have been challenging.

E

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