2 Pounder problems?

[Guest Mike]

Yes the first thing to do is to actually get through the armour. APHE that fails to penetrate because it has less kinetic energy is no better than rifle bullets.

However I think there's one thing missing from teh argument, and that is that an APHE shell that DOES penetrate and explode will generate a wider AREA of damage.

Based upon nothing other than my own surmise I would expect fragments from an AP shot penetration to have a smaller cone than those from an APHE penetration.

Hence an aPHE shell not only gets more fragmetns, but it spreads them around more of the inside of the target, with a better chance of hitting somethign vital.

Of course the difference may be utterly trivial in the wider scheme of things.....

[JasonC]

Of course I read all of it, I just didn't find much of it terribly on point. How you carry the energy to the target is not essential, and even the number of pieces made is not essential - though the latter will have a lot more to do with the total energy of the engagement than some apparently suppose.

The BAE is going to track the total energy, because even in the case of the middling shells with the most to gain from carrying some E to the target in chemical form, the KE outweighs the HE (or CE) by a factor of 4 to 8. The composition varies only in a minor way. You will get a distribution of fragment sizes and velocities either way, containing every scrap of the overall E.

Is a 37mm with an extra 50k joules from HE burster going to be better than one without? No doubt. Is it going to be better than a 2 pdr with 70k more joules to start with? No.

As for the supposed importance of practice, as though everyone knew everything, modern penetrators completely ignore bursters and simply go for the maximum muzzle energy and the narrowest cross section to apply it to. And they blow the turrets clean off the tanks they hit etc. When the engagement energy is 10-50 million joules, what difference is a few tens of grams of HE going to make? Modern tank guns are basically "mass drivers".

There is simply nothing magical about C energy compared to K energy. The K energy is emphatically not inert or one track etc. When the K energy is also an order of magnitude larger, obviously the result of the engagement is going to turn mainly on what the KE does.

[ January 30, 2007, 12:23 AM: Message edited by: JasonC ]

[Andreas]

Here's what it should look like Jeff:

The equation therefore looks something more akin to:

2-pdr AP-solid shot generates “X” number of fragments during plate perforation .

It’s behind armor fragmentation therefore equals X. It's chance of penetration multiplier = 1-6 on a D6, i.e. we assume that at a given distance, it will achieve a penetration (this is highly simplified).

2-pdr AP-HE generates “X-y” number of fragments during perforation where -y = the number of fragments lost due to loss of kinetic energy, this could be as high as X if no penetration is achieved due to the loss of kinetic energy. If it penetrates, in addition it will generate “Z” number of fragments by the bursting charge. it's chance of penetration is 2-6 on a D6. It’s behind armor fragmentation is therefore:

= X -y + Z

37mm pzgr AP-HE generates “X - y1” number of fragments during perforation, but it generates 1.5 to 1.6 times Z fragments from the bursting charge because it uses PETN instead of Picric Acid (note there is not accounting here for the larger 37mm pzgr bursting charge). It's chance of penetration is 3-6 on a D6.

37mm pzgr AP-HE behind armor fragmentation = X -y1 + (1.5Z)

For giggles lets put some arbitrary numbers to this cause' some folks don’t like “X’s” and “Y’s”, and "Zs".

Lets say plate perforation generated fragments “X” = 100 effective fragments.

Lets say bursting charge generated fragments for 2pdr APHE “Z” =100 effective fragments.

Let's say we lose 20 fragments as -y due to lower penetration performance.

2pdr Solid Shot therefore introduces 100 effective fragments into the crew compartment

2pdr APHE introduces 100 -20 + 100 = 180 effective fragments into the crew compartment

Let's say for the 37mm pzgr APHE we lose -y = 50 fragments. It therefore introduces 100 - 50 + (1.5 x 100) = 200 effective fragments into the crew compartment

Ok – quiz time:

If you wish to maximize kill probability against a tank from firing any of these projectiles, does it make more sense to:

a) Introduce 100 fragments into the crew compartment; or

Introduce 180 effective fragments into the crew compartment while risking a 17% probability of no damage; or

c) Introduce 200 effective fragments into the crew compartment while risking a 33% probability of no damage.

Answers on a postcard.

All the best

Andreas

[JonS]

Andreas, even that overstates it if the total energy of the APHE (ie, KE + PE) is less than the KE of plain AP. In that case the equations would be:

2-pdr AP-solid shot generates “X” number of fragments during plate perforation .

It’s behind armor fragmentation therefore equals X. It's chance of penetration multiplier = 1-6 on a D6, i.e. we assume that at a given distance, it will achieve a penetration (this is highly simplified).

2-pdr AP-HE generates “X-y” number of fragments during perforation where -y = the number of fragments lost due to loss of kinetic energy, this could be as high as X if no penetration is achieved due to the loss of kinetic energy. If it penetrates, in addition it will generate “Z” number of fragments by the bursting charge. it's chance of penetration is 2-6 on a D6. It’s behind armor fragmentation is therefore:

= X -y + Z

37mm pzgr AP-HE generates “X - y1” number of fragments during perforation, but it generates 1.5 to 1.6 times Z fragments from the bursting charge because it uses PETN instead of Picric Acid (note there is not accounting here for the larger 37mm pzgr bursting charge). It's chance of penetration is 3-6 on a D6.

37mm pzgr AP-HE behind armor fragmentation = X -y1 + (1.5Z)

For giggles lets put some arbitrary numbers to this cause' some folks don’t like “X’s” and “Y’s”, and "Zs".

Lets say plate perforation generated fragments “X” = 100 effective fragments.

Lets say bursting charge generated fragments for 2pdr APHE “Z” =20 effective fragments.

Let's say we lose 50 fragments as -y due to lower penetration performance.

2pdr Solid Shot therefore introduces 100 effective fragments into the crew compartment

2pdr APHE introduces 100 -50 + 20 = 70 effective fragments into the crew compartment

Let's say for the 37mm pzgr APHE we lose -y = 50 fragments. It therefore introduces 100 - 50 + (1.5 x 20) = 80 effective fragments into the crew compartment

Ok – quiz time:

If you wish to maximize kill probability against a tank from firing any of these projectiles, does it make more sense to:

a) Introduce 100 fragments into the crew compartment; or

Introduce 70 effective fragments into the crew compartment while risking a 17% probability of no damage; or

c) Introduce 80 effective fragments into the crew compartment while risking a 33% probability of no damage.

Answers on a postcard.

All the best

Jon

[John Kettler]

I think there's a logic disconnect in the conclusions being drawn about the utility of 2 pdr. AP shot vs. German 3.7 cm APHE.

I agree that if the the 2 pdr. AP shot grossly overmatches the target armor, then a highly energetic, very hot projectile enters the fighting compartment, accompanied by essentially globules of hyperplastically deformed armor, unless the armor's very brittle, as in the M-13/40 case, in which case the armor shatters rather than flows.

This represents the best case for the 2 pdr. AP shot.

With better armor quality, though, far more of the projectile's KE is used to penetrate, drastically reducing residual KE, thus reducing the damage potential of what's introduced into the fighting compartment. As armor thickens, the situation becomes even worse for 2 pdr. AP shot, for now there's even less energy left after penetration, if penetration even still occurs.

Now, let's look at the 3.7cm APHE case. In the same gross overmatch scenario I described above,

the shell smashes easily through the armor, unleashing pretty much the same armor globules or fragments as in the 2 pdr. AP shot case, then explodes, with ~ 25% less metal, but what's there is traveling at very high speeds. You might think that it would be a wash between the two projectiles in this case, but the Beda Fomm tests indicate that even here, with less and lower brisance explosive, the lethality edge markedly favors the APHE. Why? In those tests, the 2 pdr. APHE not only cleanly penetrated, but when it went off, sieved the sandbags representing the crew. By contrast, the was NO mention of any antipersonnel effects for the 2 pdr. AP shot case, merely a description of how it cracked the armor.

And that's the best case.

Where the APHE really begins to shine is when the 2 pdr. AP shot starts to suffer marked performance degradation against better and/or thicker armor.

While the APHE is going to be affected the same or more than the AP shot when it comes to secondary missile production from penetration per se, what it brings to the battle that the 2 pdr. AP shot doesn't is the ability to basically conjure up KE

just at the point where the projectile's running out of steam, and that's with no credit given for

the effects on the crew of the blast in a confined space. So now, instead of largely spent fragments entering, some quantity of white hot hardened steel fragments are unleashed at close to whatever the detonation velocity is for PETN, and it is these that do precisely the kinds of damage noted in the Beda Fomm tests, Jarrett's statement, and

the British OR study I'm still trying to identify.

Moreover, in cases in which the 2 pdr. AP shot doesn't even get clear through the armor, the APHE, in the same fix, is still lethal if even half the projectile length is inside the fighting compartment when it detonates.

I repeat the basic conclusion. 2 pdr. AP shot typically leaves a repairable tank and a largely unhurt crew, whereas a partial (as described above) or full penetration by APHE, followed by detonation, K-kills the tank and puts the crew out of commission.

There's another item which needs addressing, too.

That is the incorrect understanding of what happens when the M1A1/A2 120mm DU projectile hits

and destroys a target. It is NOT the KE from the impact that is blowing the, say, T-72 turret tens of feet into the air. Rather, it is the interaction between the pyrophoric long rod DU fragments, plus the hyperplastically displaced metal and ceramic armor array, smashing into the

exposed autoloader ammunition cassette for the 125mm gun and detonating the propellant charges, possibly the HE Frag shells and the AT-8s if aboard. It is that catastrophic explosion or series thereof which turns functional tanks and crews into flaming carcasses in milliseconds.

Regards,

John Kettler

[JonS]

Did you just eat a dictionary? Not that it matters, you analysis is still pants.

Read what ... ah, never mind. I doubt you could - or would even if you could - grok it anyway.

[Andreas]

Originally posted by John Kettler:

I repeat the basic conclusion. 2 pdr. AP shot typically leaves a repairable tank and a largely unhurt crew, whereas a partial (as described above) or full penetration by APHE, followed by detonation, K-kills the tank and puts the crew out of commission.

Then this should be borne out by comparative crew loss numbers. From having looked at Goodwood, where far better APHE than 37mm was used (admittedly against better armoured tanks, but on the whole the advantage had shifted towards the gun), I don't think the simple conclusion that APHE puts the crew out of commission stands. Loss figures in the ar,oured regiments don't support it, IIRC.

All the best

Andreas

[JasonC]

I'd be perfectly willing to accept Andreas' analysis if he divided his effective shell fragments by 10, or multiplies his KE produced ones by 10. Then it would be an accurate picture of the situation. Which is, a bit of burster helps BAE but by pretty trivial amounts, because the energy it brings to the party is pretty trivial.

To John K on the other hand, the problem with your notion of it is that you think the penetration problem makes energy go away. Nothing makes energy go away. Energy is conserved. Every joule ends up somewhere. If the round fails to penetrate, the tank rocks, but all the energy was still felt. If the round glances off, it can carry some of them away. But if it flat stops, anywhere, some other bits of matter picked up every last joule, regardless of where they came from.

Try "protecting" a pocket in billards by putting 5 balls in the way, all in a row.

[Andreas]

Originally posted by JasonC:

I'd be perfectly willing to accept Andreas' analysis if he divided his effective shell fragments by 10, or multiplies his KE produced ones by 10. Then it would be an accurate picture of the situation. Which is, a bit of burster helps BAE but by pretty trivial amounts, because the energy it brings to the party is pretty trivial.

They're just numbers I made up, personally I'd be happy with X, y, and Z, since I do not lay claim to a shred of expertise on fragment generation, other than having looked at armour plate with shot stuck in it once or twice.

All the best

Andreas

[John Kettler]

The summary conclusion for the lethality of German APHE vs. 2 pdr. AP shot is for the Western Desert, where, as noted before, the British did NOT have armored ammunition stowage containers and were campaigning fast, lightly armored tanks. As such fixes were implemented later on, this would've had the effect of lowering both K-kills and crew losses.

A much stronger leverage on the data, though, is the dramatic change in the composition of the British force on the one hand with the adoption of the far better protected Grant/Lee, followed by the Sherman, coupled with the enormous tank losses

Rommel sustained, changing the battlefield dynamics from large numbers of fast, vulnerable cruiser tanks against smaller numbers of better protected, harder hitting German tanks to large numbers of relatively powerful, well protected tanks against a handful of nasty ones, chiefly the Mark IV Special. IOW, much of the German tank fleet could no longer achieve kills because it couldn't penetrate the new, heavier tanks the Allies fielded and because there were far fewer tanks left with which to fight. 40 D.A.K. runners, some of which were Italian, vs. Monty's entire force.

I think these are really important aspects to be considered in assessing the loss data. To me, a mere graph of typical losses isn't anywhere nearly as useful as one that shows which tank types were taking what lumps and when. Even better if we knew from what.

JasonC,

I'm well aware of the energy conservation laws, just as I'm well aware of tanks shuddering when firing and when hit, KE transfer to the target tank as heat, and a number of other things. I didn't say that the KE disappeared, merely that in situations in which there wasn't enough oomph ( a very precise terminal ballistics term) to penetrate, the 2 pdr. AP shot was able to do little, if anything, against high quality armor, whereas even a partial APHE penetration and detonation typically still K-killed the tank and so cut up the crew as to render it useless as a combat entity.

Back in the 1970s, AFV-G2 magazine ran an article on armor penetration in which the various cases of

projectile and armor interaction were both discussed and shown via graphics. Sometimes the armor is too hard for the projectile and shatters the tip, preventing penetration. This was the face-hardened case. Sometimes the armor's too thick to be penetrated deeply enough to even bother the crew or else ricochets off. Both phenomena are visible in the famous shot of a King

Tiger's glacis and front lower hull. ISTR some nine different situations which could arise when projectile met armor. This link isn't that article, but does show some of what I'm trying to describe.

http://www.battlefield.ru/index.php?option=com_content&task=category&sectionid=10&id=44&Itemid=64

This is even better, not to mention has the aforementioned King Tiger picture I mentioned. Note particularly the description of what happens to uncapped AP encountering face-hardened armor.

http://www.lemaire.happyhost.org/ship/edito/11220.html

Regards,

John Kettler

[ January 31, 2007, 10:04 AM: Message edited by: John Kettler ]

[michael kenny]

That famous picture of the TII with the 'groove' in the glacis has been altered. The original untouched pic is not nearly as dramatic and the hit(if it is such)is barely visible.

[JonS]

Originally posted by John Kettler:

I didn't say that the KE disappeared, merely that in situations in which there wasn't enough oomph ... to penetrate, the 2 pdr. AP shot was able to do little, if anything, against high quality armor, whereas even a partial APHE penetration and detonation typically still K-killed the tank and so cut up the crew as to render it useless as a combat entity.

BS. APHE fragments are not going to penetrate where AP has failed.

[ January 31, 2007, 01:55 PM: Message edited by: JonS ]

[John Kettler]

michael kenny,

Wasn't aware of that.

JonS,

I think you are misconstruing what I said. I was referring to the situation in which the projectiles have so little energy left that they wind up still stuck in the armor plate, but partially protruding into the fighting compartment. Clearly, the 2 pdr. AP shot in this case isn't going to do anywhere nearly the damage it would do in cases where it grossly overmatched the target armor, whereas tests found that even a partial penetration of an APHE projectile, said penetration defined as being 50% of projectile length inside the fighting compartment, followed by detonation, still sufficed to K-kill the tank and wound the crew enough to incapacitate it.

Regards,

John Kettler

[JonS]

You are still ignoring that the APHE is bringing less KE to the party. If an AP - with it's higher KE - winds up "partially protruding into the fighting compartment", then the APHE is going to end up buried deep in the armour or scratching the paint work. In other words; doing nothing.

Conversely, if the APHE has enough KE to penetrate sufficiently to introduce fragments to the interior, then the AP is well in there, bouncing about causing mayhem.

Frankly, about the only place I can see APHE being clearly superior to AP is in very lightly armoured vehicles where an AP is likely to punch out the other side. In that case having the APHE det inside would be useful, but still the AP has introduced various spalling fragments, so it isn't a complete loss.

[John Kettler]

JonS,

No, I'm not! I clearly stated that the 3.7cm projectile weighed 25% less than the 2 pdr. AP shot, and I'm well aware of the KE equation.

From the previously cited GERMAN INFANTRY WEAPONS, p. 114,the MV for the Pak 36 is 2625 fps for AP (really, APHE) and 3450 fps for AP 40 (PzGr 40).

Per THE ENCYCLOPEDIA OF WEAPONS OF WORLD WAR II, p. 180, the MV for the 2 pdr. is 2626 fps. Both guns are listed as having an effective range of 600 yards. These are the knowns, but what I don't have is any comparison between the metallurgy and shape of the 2 pdr. AP shot and the German 3.7cm APHE, from which someone could compute the ballistic coefficients on the one hand and the penetration capabilities on the other. John D Salt and/or Jeff Duquette, can you help?

JonS,

If we're to believe your view, then how do you explain the Beda Fomm test results, where neither the 2 pdr. APHE nor the 2 pdr. AP shot was described as having penetrated clear through the target tanks and out the other side, M13/40s whose degree of armor protection was markedly thicker than what you postulate? Your scenario didn't obtain, yet the APHE clearly was markedly more effective than its AP shot confrere.

Expanding the discussion slightly, I think it would be interesting to look at the more typical case, German 5 cm APHE from the short 5cm vs. 2 pdr. AP from various British tanks. Recall that Playfair concluded in Volume 3 of the HMSO Middle East series that this gun/projectile combination

was better than the 2 pdr. firing AP shot. What I'd like to see are the same kinds of data for the 5 cm that Jeff Duquette so kindly provided for the German 3.7cm APHE. Am particularly interested in whether the German projectile was capped and maybe even ballistic capped.

Regards,

John Kettler

[JonS]

Originally posted by John Kettler:

I think it would be interesting to look at the more typical case, German 5 cm APHE from the short 5cm vs. 2 pdr. AP from various British tanks. Recall that Playfair concluded in Volume 3 of the HMSO Middle East series that this gun/projectile combination was better than the 2 pdr. firing AP shot.

No **** Sherlock. The 50mm has over 1.5 times the cross sectional area of the 2-pr.

Try apples with apples numpty.

[michael kenny]

Spot the difference............

[JasonC]

John K - sure, tanks not penetrated aren't penetrated. Check. Bitty explosive at the back of the non-penetrating round doesn't make it penetrate either.

If on the other hand the round goes in, so does the armor in its path, and they get all the E. If the shot sticks in the hull but pokes through, it has lost all its E, and the "plug" it shot out of the way has picked up essentially all of it.

The E shot into the tank is not 5% or 10% in that case, it is nearly all of it. The mass that E is distributed over is less if the round doesn't go clean in. That is about it. You don't get oomph of round minus unoomph of armor, you get oopmh of round (conserved regardless) outside the armor or oomph of round inside the armor. All a burster does is add a very modest amount to the overall oomph. The main oomph is coming from the powder burned back in the firing chamber of the shooting gun, simply because there is vastly more of it.

[Jeff Duquette]

This is sort of interesting. Here Ian Hogg is suggesting that the German 37mm pzgr projectile was slightly superior to the 2-pdr AP-solid shell because the German projectile contained an explosive filler.

Ian Hogg, “Armour In Conflict, Page 103.

“On the other side of the line the German tanks were equipped with either a 37mm high-velocity or a 75mm low-velocity gun. The Germans never used plain solid shot: with the exception of composite shot (noted below) all their projectiles carried a charge of high explosive and a base fuze, so that their 37mm gun had a slight edge over the otherwise comparable 2-pounder.”

The image below is a 35mm Oerlikon SAP-HE projectile bursting after perforation of what appears to be a 20mm or 30mm plate. Of interest is relative amount of back surface fragmentation generated – i.e. very little. Conversely the bursting charge is generating a fairly generous amount of fragmentation. Now this isn’t completely gratuitous. Moreover the SAP-HE shell has a larger bursting charge than 37mm pzgr. What this does show is that it is not a given that back surface fragmentation is necessarily particularly devastating and additional fragmentation from a bursting charge certainly can’t hurt, and may represent the lions share of behind armor effects from projectile perforation.

Again back surface fragmentation may consist of only one fragment – the projectile itself – at intermediate velocities against thin plates. This is basically a petal type failure of the plate in which no spall is generated by the passage of the projectile through the plate – ala a AP projectile passing through the thin skin of a truck or a half-track.

Backsurface spall may represent the formation of only one plug about equal in diameter to the caliber of the AP Projectile. Plug failure. Plugging represents a shear failure along a fairly well defined plane through the plate.

Or you can also get a combination failure in which a few (ala the Oerlikon image), too many fragments can be thrown off of the back surface during projectile perforation.

Either way you slice it the math is relatively simple. You can twist and turn but in the end there is spall and there is bursting charge fragmentation. 2pdr AP-solid don't get any bursting charge frag, 37mm pzgr does. So my math -- as originally presented by me -- is pretty much the math.

[John Kettler]

Jeff Duquette,

The Hogg piece is informative and intriguing, but in it he flatly contradicts what he said about the same issue in THE GUNS 1939-45.

The SAPHE photo is most helpful, but I think that what we're seeing is probably representative of more yielding armor, such as RHA, rather than, say, face-hardened plate. Combat damage shots I've seen would appear to confirm that, too.

Returning to the pic, which I can only hope shows all the ejecta from penetration but may not, what I think is useful is that its ratio of base diameter to plate thickness is of about the same order as for the projectiles and armor we're discussing, yet we see petaling, with very little pentration related fragmentation in evidence. If this is in fact representative of what was happening in the Western Desert, then the 2 pdr. shot likely WAS the principal damage agent when an Axis tank was hit and penetrated, with spall/penetration fragmentation amounting to very little, except when hitting brittle, poor quality armor.

How are you fixed for drawings and tech data on the German 5 cm short APHE projectile?

Regards,

John Kettler

[Jeff Duquette]

Originally posted by John Kettler:

Jeff Duquette,

The Hogg piece is informative and intriguing, but in it he flatly contradicts what he said about the same issue in THE GUNS 1939-45.

Precisely

The SAPHE photo is most helpful, but I think that what we're seeing is probably representative of more yielding armor, such as RHA, rather than, say, face-hardened plate. Combat damage shots I've seen would appear to confirm that, too.

The photo is the photo. It is reflective of minimal back surface throw.

FHA was of course brittle on the face -- make sure you distinguish in the photos the difference between front and back surface. The contrasts in failure mechanism between the two surfaces will typically be quite dramatic.

Only The first few mm's of FHA will be cemented(or the first few cm's depending upon the overal plate thickness). But of course the greater proportion of plate consists of a ductile backing. The back section of the plate is ductile for the specific reason of minimizing back surface fragmentation. The super hard face breaks the nose of the projectile, while the ductile backing reduces backsurface effects.

Like RHA, FHA was of course subjected to compliance standards and compliance testing. Each heat would have samples extracted for ballistic testing. British, German and American compliance standards also included both limit velocity specifications as well as backsurface spalling specifications to which the samples were expected to adhere. The latter requirement of course being to minimize back surface spall. Obviously as the war progressed German plate quality began to decline, but from what I have seen on the subject panzer armor plate in the 1939 - 42 period was generally good to very good material.

Most armor doesnt simply "explode" when a projectile strikes it, or a projectile perforates it. That sort of defeats the purpose of the armor. The Italians seem to have had problems with this as indicated by one of my previous references, conversely the same quote implies that British armor did not have the same issue. German armor -- RHA and FHA -- seems to have preformed about as well as British in this period. The various accounts of 2-pdr AP penetrating German panzers and the panzer continuing to move and fight -- at least to me -- suggests back surface effects of these penetrations were not particularly dramatic.

How are you fixed for drawings and tech data on the German 5 cm short APHE projectile?

[/QB]

very well. i actually have a 5cm pzgr projectile in my collection -- as well as sectional drawings, firing tables, testing data, blah blah blah. i'll post something latter on this projectile.

[ February 02, 2007, 05:59 AM: Message edited by: Jeff Duquette ]

[John Kettler]

Jeff Duquette,

Went back and looked at that SAPHE detonation pic. There's hardly anything happening on the front of that panel at all, so am wondering whether it might be some sort of hardened plate, rather than RHA. Was any info on this provided from wherever you got the pic? Also, are we sure the target plate is steel? Somewhere in my files I have a photocopy of the Gepard manual, in which are several shots illystrating the effectiveness of what I recall as the 35mm Oerlikon KDA mine shell. The target in that instance was aluminum plate, illustrating how it penetrated the aircraft then blew up interior structure and components.

Don't know where you found all your goodies, but color me impressed. Used to know a guy who co-owned a small firm which sold tear gas and the like to police departments, and he had a nice range of cartridge casings up through German 128mm

and as small as a modern case for the experimental 25mm cannon.

Appreciate the post to come on the 5 cm short APHE. BTW, was the same projectile used for the 5cm lang?

Regards,

John Kettler

[Jeff Duquette]

Attached is a sectional of 5cm pzgr.39. The explosive filler weight is listed as 0.027Kg – which I assume includes the booster weight (or the gaine for the British speaking members of the audience). The British War Office Intelligence series on enemy ammunition lists the filler as being 14dr of an 87/13 blend of PETN & wax. or ~0.025Kg of PETN\wax.

The uncapped 5cm pzgr, which predates the pzgr39 -- used a smaller bursting charge – 0.017Kg – also PETN\Wax.

Best Regards

JD

[MikeyD]

I recall an earlier CMBB discussion about 45mm gun ammo. The poster had stated that as the war progressed Russia transitioned from 45mm APHE to straight AP. He concluded from that that they had dropped the HE fill due to negligable effect. My alternate take on it was that the HE fill was dropped because its only useful if you achieved penetration! First they had to concern themselves with successfully piercing an 80mm PzIV hull front, after that they can consider behind-armor effects. By mid-war the obsolescent 45mm gun simply needed the kinetic punch of solid shot to achieve its minimum aims.

Talk about thinner armor properties, I believe (based on pre-war press) the M1114 armored humvee uses a dual-hardness laminate sandwich steel. A hard layer on the outside and a more ductile steel at the back that's less likely to spall. God knows how the more exotic added armor layers work.

[Jeff Duquette]

Originally posted by MikeyD:

I recall an earlier CMBB discussion about 45mm gun ammo. The poster had stated that as the war progressed Russia transitioned from 45mm APHE to straight AP. He concluded from that that they had dropped the HE fill due to negligable effect. My alternate take on it was that the HE fill was dropped because its only useful if you achieved penetration! First they had to concern themselves with successfully piercing an 80mm PzIV hull front, after that they can consider behind-armor effects. By mid-war the obsolescent 45mm gun simply needed the kinetic punch of solid shot to achieve its minimum aims.

I don't know what the previous poster may be referring to. I may be wrong on this, but I think all of the marks of 45mm APBC used a small bursting charge. On the other hand, 45mm APC -- as far as I know -- never included a bursting charge. Some of this might be attributable to developing training rounds that aren’t leaving explosive charges on training ranges. I mean it’s all sort of interesting, but a bit vague.

As to dropping the bursting charge on the part of British for their AP -- I don't disagree that the ability to perforate more armor than AP-shell was as likely a motive as any -- and I said as much several times fairly early on in this thread. The other motive was probably associated with the Germans use of spaced armor add-ons and British tests on spaced plates -- and picric acid can be fairly touchy to shock and friction of impact under certain conditions. AP-shells had a tendency to explode between plates resulting in a much reduced penetration capability. Another motive may have been that is much easier to produce solid shot than it is to produce AP-shell. The point is of course, that there are a number of possible motives that do not necessarily equate to the argument that the British used AP-solid shot because it was as effective in behind armor effects as AP-shell. And in spite of all the twists and turns in thread, the point originally being argued regards behind armor effects and what one might expect in behind armor effects for AP-shell and AP-soild. Behind armor effects presume perforation has occured. Arguing about penetration capability by a specific projectile is alway interesting, but as I see it, sort of tangent to the original intent of this disscussion.

Regarding modern armor and laminates and spall liners and such -- we are now talking about a wide range of potential threats which will have an equally wide variety of potential behind armor effects. For example a tungsten carbide (WC) core AP bullet will pretty much shatter following plate perforation. Makes for excellent behind armor fragmentation. In addition thin HHA plates(not to be confused with FHA) are often used when the the design threat is small arms or medium caliber projectiles. High Hardness Armor or very high hardness armor is very efficient at breaking up projectiles or enhancing richochet potential. But they are also more brittle than RHA. In defeating a small caliber projectile the low ductility can result in some back spall. This is easily delt with via a light weight spall liner.

The WC core, in and of itself generates a large amount of secondary fragmentation into a confined crew compartment. The same sort of thing is associated with APCR or HVAP or APDS using WC cores. The cores themselves consist of very heavy and very brittle material that invariably shatters following plate perforation. Behind armor effects associated with the WC core shattering are therefore good or very good.

Same again is associated with WHA rods or DU rods or HEAT. The very high impact velocity associated with long rod penetrators -- 1.4Km/s(+) -- will generate large amounts of secondary fragmentation from both plate spall as well as the secondary fragmentation from the penetrator break upon. HEAT perforation will also potentially throw a large amount of very high velocity spray from the jet into the crew compartment -- dependent upon the magnitude of "over penetration" associated with the jet and armor it is defeating. The point here is that hydrodynamic perforation associated with WHA or DU LRPs or shaped charge jets or EFPs or whatever and their associated behind armor effects are not nessecarilly reflective of the sort of behind armor effects associated with much slower, full caliber ductile steel projectiles vs. monolithic ductile steel targets.

I mean don't get me wrong -- steel plates and steel projectiles will spall and shatter and generate secondary fragmentation. But this can be minimal or it can be alot (ala Italian tank armor).

Best Regards

JD

[ February 02, 2007, 10:09 AM: Message edited by: Jeff Duquette ]