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2 Pounder problems?


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Originally posted by Stalin's Organist:

4 F-86A's experimentally armed with 20mm cannon were trialed in January 1953 and 282 combat missions flown - see Joe Baughers F-86 page

Interesting. Well I stand corrected. Thnx for the link. I didnt look too closely, but were any of these F-86 involved in air-to-air combat -- any confirmed air to air kills?

[ January 28, 2007, 07:16 AM: Message edited by: Jeff Duquette ]

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The passages from Jarrett John K seems to have agreed are his source are, let us be clear, not OR studies (MELF stands for Middle East Land Forces, btw, John), they are personal observations. When I read them I took them to be an indication of the need to improve ammunition stowage to prevent "brew-ups", and on re-reading they still seems to say the same. British tank desgners took up a policy to deal with this problem, adding armoured stowage bins and declining to stow ammunition above the turret-ring.

[/QB]

I’m not sure I understand your first sentence. They are personal observations so they hold less weight? Is that your point?

Ok, so they added stowage bins and added encased ready racks or whatever. Good idea. But how does this equate to bursting charges being ineffective? If they added storage bins maybe it was because bursting charges were effective?

If the passages were really intended to convey the message that APHE is a crew-killing wonder-weapon, then I am at a loss to explain why nobody in the OR or tank design communities ever (as far as I know) called for APHE to be adopted for land service, or why the supposedly fearsome destructive qualities of APHE mysteriously escape mention in all the personal recollections of British tank crew members (Joly, Crisp, Tout, Foley, Wilson, Farrell, Hills, Dyson -- there are quite a few of them).

All the best,

John. [/QB]

The British did use bursting charges in the early version of 2-pdr AP. It's commented upon in one of those bits I quoted from Jentz. I also have a scale sectional of 2pdr Mk-I AP-HE projectile laying around here in my junk somewhere. In addition, I think you commented earlier upon 3-pdr AP-HE -- I assumed you were refering to the 3pdr tank gun. It seemed to have been used by the Land Service early on. But of course its use was discontinued early on as we dont see bursting charge in later marks of 2-pdr, or in 6-pdr or 17-pdr. But this doesn’t lead to the conclusion that behind armor effects of AP-HE were ineffective. And I find no reason to disbelieve master Jentz ;) . Moreover discontinued use by the British, as I have already stated, appears to be associated with the ability of AP-solid to perforate more armor than AP-HE. In addition, AP-HE has a tendency to predetonate if spaced armor is employed -- and the Germans were using spaced armour on later versions of the Mk-III (and I think Mk-IV).

Regarding Crisp and the like, lack of evidence is now evidence? Nobody mentioned it therefore it's not effective? Maybe it wasn't mentioned because the guys that were most effected by bursting charges weren’t around after the fact to comment upon the effectiveness or lack thereof.

All your doing is reiterating that the British had a different philosophy on this subject than the US, Germans, Russians and Italians. Why would I be inclined to think the British approach in using solid shot is more valid than any of these other group of folks and their use of AP-shell? The fact that British experience with AP-shell was poor doesn’t help to bring me to a conclusion that the same is true for US, Russian, German or Italian AP-shell.

[ January 28, 2007, 07:14 AM: Message edited by: Jeff Duquette ]

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I have dug quite deeply in my way less than exhaustive references and other than Hogg, have naught to show for the 3.7 cm APHE's exact explosive load, but I do have a data point for comparison. From Hogg's AMMUNITION, p. 149 in the drawing of the 3" shell with Projectile, fixed, A.P.C. M62 with fuze BD M66A1 and Tracer. Explosive filler is listed as 0.14 lbs. Explosive "D."

Regards,

John Kettler [/QB]

I think I indicated the weight of the 37mm pzgr bursting charge in one of my above posts.

37mmpzgr001rf9.th.jpg

37mmpzgr002sj5.th.jpg

37mmpzgr003kb4.th.jpg

[ January 28, 2007, 07:13 AM: Message edited by: Jeff Duquette ]

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The following is an interesting snippet from one of those overview papers on Armour Penetration. Dunno the exact title of the document as I only have scans of bits and pieces, but it is apparently kept in the Bovington Tank museum archives – something to the effect of Armour Penetration or some such thing.

My interpretation – which would of course be considered jaundiced by some given my stance on this topic – is that Italian armor was resulting in a large amount of fragmentation from projectile perforation. In this instance a bursting charge would probably add little in the way of behind armor effects – unless of course you are of the opinion that a tank crew needs to be killed twice or three times.

On the other hand it seems to imply that good quality British armor was not spraying crews with armor plate spall from projectile perforations. Perhaps I would want a bursting charge that functions properly in this instance.

bovingtondocumentjk9.th.jpg

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Originally posted by Jeff Duquette:

I’m not sure I understand your first sentence. They are personal observations so they hold less weight? Is that your point?

My point was that something that does not follow the method or discipline of OR should not be misrepresented as being an OR study.

Originally posted by Jeff Duquette:

Ok, so they added stowage bins and added encased ready racks or whatever. Good idea. But how does this equate to bursting charges being ineffective? If they added storage bins maybe it was because bursting charges were effective?

Oh, doubtless they were. However, that APHE was effective in setting unprotected ammunition on fire does not necessarily imply that AP was less effective, which is the inference you seem to be drawing.

Originally posted by Jeff Duquette:

The British did use a bursting charges in the early version of 2-pdr AP. It's commented upon in one of those bits I quoted from Jentz.

Yes indeed, I rather fancy I raised this point myself.

Originally posted by Jeff Duquette:

In addition, I think you commented earlier upon 3-pdr AP-HE -- I assumed you were refering to the 3pdr tank gun. It seemed to have been used by the Land Service early on.

Indeed, but this was a considerable time before the 1941-42 experience on which ammo stowage policy was later based, was it not?

Originally posted by Jeff Duquette:

And I find no reason to disbelieve master Jentz ;) .

Nor do I. But I should be grateful if anyone who thinks that Jentz is supporting John K's portrayal of APHE as a wonder-weapon could point out where, precisely, Jentz claims that the fires suffered by British tanks when hit were due to the ammunition nature rather than the ammunition stowage policy.

Originally posted by Jeff Duquette:

Moreover discontinued use by the British, as I have already stated, appears to be associated with the ability of AP-solid to perforate more armor than AP-HE.

This seems to directly contradict Hogg's statement about the apparent lack of improvement in BAE with the 2-pounder.

Originally posted by Jeff Duquette:

Regarding Crisp and the like, lack of evidence is now evidence?

No, anyone who has spent any time arguing with John K knows perfectly well that absence of evidence is not evidence of absence. They also know where that line of reasoning ends up, sooner or later.

Originally posted by Jeff Duquette:

Nobody mentioned it therefore it's not effective?

If it was as effective as John K claims, then I find it very surprising indeed that it has escaped comment to the degree it apparently has. Or maybe there are such comments, and I've missed them.

Originally posted by Jeff Duquette:

Maybe because the guys that were most effected by a bursting charges weren’t around after the fact to comment upon the effectiveness.

Maybe. In which case, one would expect to see figures showing a higher proportion of crew casualties in knocked-out British tanks than German ones knocked out by British shot. If anyone has such figures, I'm all ears.

The figures I have on percentage crew casualties from British vehicles do not seem to show significantly higher lethality from penetrations by German ATk guns (most of them presumably firing APCBCHE) than from "Bazooka" (Panzerschreck and Panzerfaust). That may not be a fair analogue to AP, as the HEAT penetrator is going in very much faster than any AP round would. It would be interesting to know if the Germans suffered less than an average of about one killed and one wounded per tank knocked out by solid shot.

Originally posted by Jeff Duquette:

All your doing is reiterating that the British had a different philosophy on this subject than the US, Germans, Russians and Italians.

That's not all I was doing, I was also pointing out that merely counting fragments disregards their distribution in time and space.

Originally posted by Jeff Duquette:

Why would I be inclined to think the British approach in using solid shot is more valid than any of these other group of folks and their use of AP-shell?

Because the British were the only power to try both natures, and abandoned APHE? As far as I know, everyone else went for APHE all through, although the Russians filled in the BR-240 burster cavity to produce BR-240SP, which suggests to me that they didn't think the burster worth the trouble in 45mm calibre.

Originally posted by Jeff Duquette:

The fact that British experience with AP-shell was poor doesn’t help to bring me to a conclusion that the same is true for US, Russian, German or Italian AP-shell.

Although British policy on ammunition natures (and other things, too!) looks idiosyncratic, I don't personally think that the behaviour of delay fuzes and bursting charges undergoes enormous changes from one nationality to another. It may be that the 2-pounder APHE was simply a bad design, from which an over-general conclusion was drawn and then never changed (like the British Army's habit of breaking step when crossing bridges, a pointless practice based on a single unpleasant experience). However, given one data point that clearly says APHE was no better than AP, and as far as I can see none that clearly say the reverse, it seems to me obvious what the sceptical observer would conclude.

As ever, we need more data.

All the best,

John.

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John D Salt,

Good stuff and much appreciated! Must keep the difference between MELF and MILF clear!

From the sum total of what I've read, there were two principal aspects to the 2 pdr. AP shot lethality issue: terminal effects on the tank, and crew casualties. One of the drivers in the former was the accessibility of stored ammunition, especially the more vulnerable propellant holding brass, to frag penetration and subsequent fire. Those armored storage bins the Germans had thus prevented outright many spall/penetration fragments from becoming potential tank killers. The U.S., for example, didn't "get religion" on this issue until the so-called "Wet" Sherman models arrived. It is precisely because of the German observation, by Tunisia, methinks, that a hit Sherman generally became a burning Sherman that the Germans called them Ronsons and Tommy cookers and felt sad for the men forced to fight in them.

The other issue was 2 pdr. shot lethality given a penetration. The 2 pdr. was quite capable of ripping an Italian tankette or tank apart and killing it. Not only was the armor thin, but it was riveted (joints sprang open when hit, shearing rivets wholesale, creating secondary missiles in the fighting compartment, much like what happened to the early Grants later on), but per the excerpt Jeff Duquette provided, the armor was apparently brittle, not ductile, and spalled badly when hit.

All in all, bad for Italian tank crews!

The above did not hold for the 2 pdr. vs. German tanks, though, for a number of reasons. We've already discussed ammo bins, but let's move back a bit. German armor was solidly welded, hence created no flying rivets. It was of high quality, hence produced little spall when nearly penetrated or penetrated, which helped keep the crew alive

and functioning. It was generally thicker than what the Italians had, too, making it harder for the 2 pdr. to penetrate in the first place. Certainly in the case of the Panzers III and IV, the internal volume was much greater than in the Italian tankettes and tanks, creating more protected zones inside which men/components were safe from the effects of a shot or shots. This aided both tank and crew survival. And all of these are before the Germans trumped the 2 pdr. outright, at least vs. the III and IV on certain models nose on, by introducing face hardened add-on armor, which defeated the uncapped 2 pdr. projectile's nose.

The sum total of these factors explain, IMO, why the British saw their AT lethality plummet once D.A.K. arrived and got going, let alone started bringing in improved gear later.

What Jarrett and Jentz both said about behind armor lethality is clear and cutting. 2 pdr. penetration generally neither K-killed (brewed up) the tank nor clobbered the crew, whereas the APHE the Germans were using did. If we can ever find the vexed British OR study, that point will be made terribly explicit, for whoever wrote it minced no words whatsoever.

Paraphrasing, any German AP shell hit which penetrates and detonates or partially penetrates such that half of the projectile body emerges into the fighting compartment before detonating, generally destroys the tank outright and wounds the crew so badly as to render it useless. Also, as noted in that chapter link posted from the Ordnance volume, by Volume III of the Middle East series for HMSO, Playfair had concluded that even the German short 5 cm gun outpenetrated the 2 pdr, which wasn't realized when the earlier volumes were written. Thus, at the common gun level, the Germans had both a penetration and a lethality advantage, to which must be added the issue of gunsights.

Jeff Duquette,

Would love to see your library! Better material than I dared hope for! What I was originally trying to do was arrive at an estimate of APHE fill ratios, but now we don't have to. Further,

since we now know the exact weight and type of burster explosive, we are now in a position to make at least first order comparisons between your 20mm M97 HEI projectile and the German 3.7 cm APHE. That, in turn, should allow us to make some reasonable deductions about what it would be like

were the latter to come acalling.

Since you know burster size, weight; can presumably derive explosive power, and know the velocities, masses and mass distribution for that 20mm shell, you can compare the known values there with the computed ones for the 3.7cm. Certainly, if we hold assumptions identical (not exactly valid, given that "I" in the 20mm's nomenclator and the fact that HEI's wall thickness can be much less than those of the APHE because of greatly reduced dynamic loads), we ought to be able to determine total explosive force being applied, the brisance thereof, and determine the consequent total fragment mass.

We can then go on to make some reasonable predictions of likely fragment size, velocity and mass. I'd expect that the fragments from the 3.7 cm. APHE detonation would be both larger than the M97's and traveling much faster, in turn, translating into much greater damage potential vs. the tank and much greater wounding potential vs. the crew. Ballpark frag size estimate would be ~ 3-4 X that of the M97 based on wall thickness alone, probably more. I say that having had the opportunity to see the inside of 20 mm AP and see the wall thickness for myself. Doubt the HEI would be much thicker. If we have good metallurgical data for both projectiles, we can also learn some things about shattering characteristics as a function of tensile strength and explosive used, allowing us to gain some insights there as well.

Having watched a lot of high speed detonation footage, I can also say that when the 3.7 cm shell detonates, it first balloons out such that the body contour will closely follow the arc described by the ogive, creating an American football shaped thing at the point of projectile body disintegration. And it is from this particular geometry that the whole fragment spray really occurs. Simple mental imaging tells us, therefore, that when this thing goes off, perhaps optimistically presuming the blast doesn't puree the crew to begin with, little of the explosive force will be applied to the nose, but its big, massy, and still has its residual KE. Where you really don't want to be, though is in the annular region of from ~45 degrees plus or minus fore and aft of the shell's axis of flight.

Restated, if hit with AP shot, don't be right in front of the penetration path or close to it. If hit with AP shell, though, and most of the momentum has been scrubbed off, you don't want to be to the side of the projectile when it detonates. And here, IMO, is where the deadliness

of APHE comes from. AP shot does all of its damage by KE, whereas APHE supplies its own. If the AP shot barely penetrates through, it does little, as evidenced by that Panzer IV/D driver I described earlier, whereas an even more marginal case by the APHE brings with it the ability to create an explosion in a highly confined space, followed by a tank filled with whizzing, heavy chunks of high grade steel which macerate men and equipment alike. Woe betide all concerned if the tank's ammo is hit by one of these white hot frags in the process!

Of course, APHE is only deadly if it can at least partially penetrate before detonating. If the gun/projectile combo is marginal against the target, or the target's armor would otherwise defeat the APHE, or the fuze can't be trusted, then it may make sense to revert to AP shot of some sort, as the British later did with American supplied 75mm APHE by removing fuze, I believe, and filling the void. Don't know whether they actually removed the burster proper. Maybe it was desperation which drove them to ignore their own direct experience of both being hit by and firing with great success German 75mm APHE. Recall the conclusion from Gazala that a German tank hit by the converted ammo was a tank destroyed.

In closing, I should also address the fuzing delay issue. There were times in which the fuze either failed to function against light armor or went off late. Over at www.tankbooks.com for example, there's a terrifying anecdote told by an M5 Stuart crewman in which the recon tank pops around a bend, sees an 88 at spitting distance, and takes a round smack through the turret side before it can even reverse. Somehow, it went clear through and out the far side, harming no one and doing nothing to the tank other than greatly improving cross draft ventilation. I've seen similar stories for Shermans hit by 88s and 75s, too. No doubt, the British annals have similar stories. These sorts of happy outcomes seem primarily to occur in situations where the impacting projectile grossly overmatches what it hits, so that the fuze timing

suddenly winds up happening in a new,greatly compressed and unworkable for the fuze timeframe.

Just to show you that the issue didn't suddenly go away after the War, I cite the remarkable design example of the Russian AA-6 ACRID air-to-air missile (on the MiG-25 FOXBAT), which was designed to kill the Mach 3+ B-70 head-on, at cumulative closing speeds of Mach 6+. This didn't give the fuze much time at all, so the Russian missile designers came up with an ingenious solution. They put the warhead at the very back and the rocet motor in the middle, exhausting to the side through angled nozzles. In this way, they gave the fuze the best possible conditions to create an optimum burst despite hypersonic closing velocities. A buddy of mine was in deep doo doo with the intel agencies for years because this contradicted the party line on how the AA-6 was put together, but he was ultimately proven right.

Regards,

John Kettler

[ January 28, 2007, 09:07 AM: Message edited by: John Kettler ]

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In regards to the delay and estimation of the shell travelling 6 feet within the tank I think you fail to take into account a couple of things. First, dependant on range of course, the round isn't travelling at 2,000 FPS when it gets to the target. Second, and IMHO more important, it isn't going 2,000 FPS after striking and penetrating the armor.

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civdiv,

Fair point!

Jeff Duquette,

I just had a Eureka! moment awhile ago when I remembered something potentially very useful from my Hughes days. Back in the late Seventies or early 1980s, the Russian surface fleet became a major threat, and the Navy found itself in the embarrassing position of not having proper munitions to kill ships and was forced to improvise with things like the Skipper, a laser-guided 250 lb. bomb with wings and a Shrike rocket motor in order to not get eaten alive by ship based AAA and SAMs. On my end, we did a crash analysis of the still in dev Maverick MAW (Maverick Alternative Warhead) as a shipkiller.

Maverick MAW was developed for the Marines as a CAS weapon, used imaging infrared (IR) guidance, and had a 300 lb. blast/frag warhead. This was how I got exposed to the Project Thor equations (q.v.) developed by Bernier

http://www.bahdayton.com/surviac/archive/surviac_bulletin/bulletin_9802/page1.html

Basically, these equations addressed the damage potential to structures (and men?) from fragments of various materials and sizes, traveling at different velocities. Thus, given fragment X, at velocity Y, will it penetrate structure Z with the following material properties? I didn't get into it very deeply, being chiefly involved in figuring out how deep into the ship various weapon installations went for purposes of determining target size, aimpoints and the like, but I did help out for a few hours using a simple program our weapon analyst made and loaded into my calculator. What we were interested in was fragment capability to pierce bulkheads, overheads, and hull, not to mention piercing missiles and torpedoes in their launch tubes, penetrating gun houses and the like.

The above seems to be to be very much along your lines of interest. Further, I remembered two other things. Blast studies are conducted by converting all explosive yields into TNT spherical charge equivalents, and you already know that blast goes up as the cube of the TNT charge weight equivalent. The other item is that the AGM-45 SHRIKE antiradiation missile had as its primary destruction element, a warhead whose frag portion was composed of thousands of 1/4 inch tool steel cubes. This design was carefully chosen because the frag size allowed for lots of fragments, each capable of ripping into a radar control cab and wrecking whatever it struck inside, while shredding above it the radar antenna, feedhorn, waveguides, etc. Given this, it seemed to me that this might be a good first order approximation for the, er, APHE experience.

In fact, it may, based on your drawings and photos of the 3.7 cm shell, be understating frag size, but even so, should give you something with which to work. Wounding potential methodology is well established (if it'll pierce 1" pine, it'll incap a man), so all you'd really need for a quick study would be cartridge casing wall thickness and material, for that issue is what drives overall APHE lethality, ammo vulnerability. Got any 2 pdr. AP round sectional drawings?

Regards,

John Kettler

[ January 28, 2007, 12:02 PM: Message edited by: John Kettler ]

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We have Hogg and we results from some test at Beda Fomm. The two conclusions are at odds with each other. We know the Jentz thingie is based upon some sort of ad-hoc tests conducted by 2nd R.T.R. at Beda Fomm. I assume we haven’t a clue on the source of Hogg’s premise?

To Recap:

======================================

"Shell, AP, Mk. 1. This shell was part of the original specification for the gun, and was a piercing projectile with a tiny filling of Lyddite and the Base Fuze No. 281, which carried a tracer. Experience revealed that on impact, the fuze tended to part company with the shell and thus fail to initiate the filling. Moreover, even when it worked correctly it appeared to do no more damage than a plain steel shot, which was easier to manufacture. As a result, the AP shell was withdrawn."

=======================================

=======================================

4.1.1.1 BRITISH GUNS AGAINST AXIS TANKS

Directly after the battle of Beda Fomm, the 2nd R.T.R. conducted tests to determine the vulnerability of the Italian M. 13-40 tanks. They reported on 14 February 1941: During the morning tests were carried of the effect of the two types of 2-pounder ammunition on Italian M13 tanks. These tests proved that the yellow painted explosive armour piercing projectile penetrates the armour at 900 yards and bursts inside with very destructive effect. Sand bags placed on the crew's seats were well riddled with splinters. The black painted solid A.P. projectile also penetrates at 900 yards and causes large cracks in the armor.

=========================================

On the differences between 37mm pzgr & 2pdr AP-HE:

The Germans apparently used Pentaerythrite Tetranitrate in the bursting charge for 37mm pzgr. PETN didn’t really evolve until after WWI. The brisance of PETN is pretty high. Higher even than RDX. It’s about 166% that of TNT.

Lyddite…hmmm Picric Acid. A throw back to the Great War I think – pre-Great War actually. Picric acid has a much lower brisance than PETN. It’s brisance is about that of TNT – or about 100% -- which is good, but certainly well below PETN.

Picric Acid can apparently combine with moisture or other metals to form rather unstable picrates. Picrates are apparently very sensitive to shock and friction. Moreover they tend to go boom under shock -- like a high velocity impact maybe. No idea if this contributed to the British problems with bursting charges or not. But it is interesting. In fact the British War Office manual on Ammunition “Text Book of Ammunition, Pamphlet No.1 Explosives” (dated 1944), page-24 indicates the following about Lyddite (or picric acid):

“Picric Acid is not always sufficiently insensitive to withstand impact on armour, and it is therefore unsuitable for armour-piercing projectiles.”

Well **** howdy – let’s put it in our armour piercing projectiles anyway ;) WTF? See the attached scan below.

ukexplosivesmanualpicricv3.th.jpg

Do we have a weight for the picric acid bursting charge in 2pdr MkI AP-HE. Anyone – Anyone – Buller? I have the scale sectional shown below -- from a German UXB manual. The bursting charge cavity for the 2pdr MkI looks somewhat smaller than that of 37mm pzgr. But this could be my imagination. In lieu of a bursting charge weight, a specific gravity or density for picric acid might be helpful. The weight of the bursting charge could than be back calculated.

2pdrmk1apheyh7.th.jpg

[ January 28, 2007, 12:42 PM: Message edited by: Jeff Duquette ]

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Originally posted by civdiv:

In regards to the delay and estimation of the shell travelling 6 feet within the tank I think you fail to take into account a couple of things. First, dependant on range of course, the round isn't travelling at 2,000 FPS when it gets to the target. Second, and IMHO more important, it isn't going 2,000 FPS after striking and penetrating the armor.

This is a good point and I totally agree with you bringing it up. Although to be fair John S. does make an attempt to futz around with residual velocities in the next paragraph. I didnt want to touch it cause I wasnt sure if Naval fuzes use longer delays or not.

There maybe something there or there may not. I think he's trying to put some numbers to this thing. Often putting numbers to these sorts of things will put them to rest.

[ January 28, 2007, 11:54 AM: Message edited by: Jeff Duquette ]

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Originally posted by John Kettler:

civdiv,

Fair point!

Jeff Duquette,

I just had a Eureka! moment awhile ago when I remembered something potentially very useful from my Hughes days. Back in the late Seventies or early 1980s, the Russian surface fleet became a major threat, and the Navy found itself in the embarrassing position of not having proper munitions to kill ships and was forced to improvise with things like the Skipper, a laser-guided 250 lb. bomb with wings and a Shrike rocket motor in order to not get eaten alive by ship based AAA and SAMs. On my end, we did a crash analysis of the still in dev Maverick MAW (Maverick Alternative Warhead) as a shipkiller. This was how I got exposed to the Project Thor equations (q.v.) developed by Bernier

http://www.bahdayton.com/surviac/archive/surviac_bulletin/bulletin_9802/page1.html

Basically, these equations addressed the damage potential to structures (and men?) from fragments of various materials and sizes, traveling at different velocities. Thus, given fragment X, at velocity Y, will it penetrate structure Z with the following material properties? I didn't get into it very deeply, being chiefly involved in figuring out how deep into the ship various weapon installations went for purposes of determining target size, aimpoints and the like, but I did help out for a few hours using a simple program our weapon analyst made and loaded into my calculator. What we were interested in was fragment capability to pierce bulkheads, overheads, and hull, not to mention piercing missiles and torpedoes in their launch tubes, penetrating gun houses and the like.

The above seems to be to be very much along your lines of interest. Further, I remembered two other things. Blast studies are conducted by converting all explosive yields into TNT spherical charge equivalents, and you already know that blast goes up as the cube of the TNT charge weight equivalent. The other item is that the AGM-45 SHRIKE antiradiation missile had as its primary destruction element, a warhead whose frag portion was composed of thousands of 1/4 inch tool steel cubes. This design was carefully chosen because the frag size allowed for lots of fragments, each capable of ripping into a radar control cab and wrecking whatever it struck inside, while shredding above it the radar antenna, feedhorn, waveguides, etc. Given this, it seemed to me that this might be a good first order approximation for the, er, APHE experience.

In fact, it may, based on your drawings and photos of the 3.7 cm shell, be understating frag size, but even so, should give you something with which to work. Wounding potential methodology is well established (if it'll pierce 1" pine, it'll incap a man), so all you'd really need for a quick study would be cartridge casing wall thickness and material, for that issue is what drives overall APHE lethality, ammo vulnerability. Got any 2 pdr. AP round sectional drawings?

Regards,

John Kettler

Hi John:

I do have a large amount of material on fragment penetration of various materials and some material on wound ballistics – although the latter is not really my cup of tea beyond having some cursory background knowledge.

When I say "Effective Fragment", it is relative to the fragments ability to generate a penetrating wound into a human. The 20mm M97 generates more than 111-fragments on average. It’s just that only 111 are deemed to have sufficient energy to wound or kill someone.

The pine board and straw board methods of determining effective fragmentation were one way of doing things. Obviously wound ballistic tests and associated algorithms have developed a long way from WWI and WWII. But the rule thumb used to be 58-ft-lbs of energy at impact. The British rounded it 60-ft-lbs (or maybe the British value reflects what it would take to penetrate a Scot). You still see studies that bandy this number around. The original source dates back to German shrapnel ball testing that predates WWI (and I don't mean shell fragments -- I mean tests with lead shrapnel balls). In that sense this number is valid, but you need to be careful in its application as it is specific to a certain fragment mass and areal footprint. I worked it out sometime ago and figured the impact velocity was about 360-fps for an approximately ½” diameter lead shrapnel ball (about 190-grains).

But a major league baseball pitcher (I guess this might be a bowler in Cricket) can hit you with a moderately fast pitched ball and deliver a blow with 58-ft-lbs of energy. The baseball hit won’t usually kill you nor do much beyond give you a bad bruise. So you need to think of the energy requirement for an effective fragment in terms of energy density. Sort of like a gal in high heels and the amount of pressure she is exerting to the tip of that high heel relative to if that same gal were wearing bozoo the clown shoes.

Regards

JD

[ January 28, 2007, 01:05 PM: Message edited by: Jeff Duquette ]

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Jeff Duquette,

Now, we're getting somewhere! If you can somehow scale the two shell blueprints so they're to a common scale, then you can quickly get a pretty good idea of the volumetric differences for the burster charges--especially if you have a micrometer, a graduated cylinder, and some clay.

For the record, on the German drawing of the 2 pdr. APHE the only part that need concern you is the portion labeled Sprengladung, or "explosive charge." The Zund thing is part of the fuze. Be sure, though to factor in any significant explosive density differences into your ruminations on the two projectiles.

Picric acid as APHE filler and shock sensitive, too? Stellar!

Excellent insight on the brisance of PETN vs. Lyddite and TNT! I'd strongly suspected that PETN was nastier than TNT, and now I know for sure. Given this, we can reasonably expect the German 3.7cm APHE's detonation and consequent effects to be considerably more effective than the 2 pdr. APHE against which we are comparing it. In light of what you've turned up, I'm starting to wonder whether Hogg was having a bit of a brain interrupt when he made his statement about no difference to the recipient between shot and shell in the 37mm/2 pdr. size range. The Beda Fomm tests alone prove he was wrong, never mind Jarrett, British OR, etc.

Regards,

John Kettler

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Jeff Duquette,

I know exactly what you're talking about regarding

the difference between simple energy delivery and an effective hit. In fact, I'll take your high heel example and run with it, for it was based on something that really happened in the early days of airliners. To save weight, lightweight structures (aluminum honeycomb, I think) were used for aircraft cabin floors and were perfectly adequate for normal foot traffic. As it turned out, the aircraft designers never envisioned big women wearing spike heels. The result? Pierced cabin floors and stuck, embarrassed ladies!

Likewise, the other day I saw a program on less than lethal weapons in which a weapon whose projectile mass and velocity would normally have been lethal was converted to a disabling round by the simple, ingenious method of fitting the hard plastic body with a crushable foam nose. The resultant weapon, at design range, will hit you hard enough to make you stop immediately, both from impact and because it'll really smart, but barring, say, your bending down at the wrong time

and getting it in the temple (target's the chest),

won't do any major damage. The planned use is to take out the ringleaders and inciters in demonstrations and riots without hurting others nearby.

Another good one I know was in one of Richard Simpkin's books on tank design. He explained the KE content of a modern tank round (British 120 rifled cannon on a Chieftain) as being the equivalent of a Greyhound at 45 kmh hitting something, but with all that impact force applied through a superhard, sharpened spike only 40 mm

wide. Painted an indelible picture with that example!

Am also fond of the differences among being hit with a boxing glove, bare knuckles, and a karate strike. It all comes down to how much force is delivered, over what unit time, to how small an area. Fundamentally, AP penetrates, in the simplest case, by hitting so hard over a very small area that it causes the armor to either flow aside (RHA or normal plate) or crack and shatter as the projectile punches through (face hardened armor). For the former, look at just about any holed Sherman pic. For the latter, dig out a pic of the flank of the IWM's Jagdpanther, where the shatter cracks are clearly in evidence.

I think it's most interesting that in the Beda Fomm tests the evaluators report armor cracking for 2 pdr. shot, but signally fail to mention the kind of sandbag perforations so clearly noted regarding the 2 pdr. APHE live fire test. This strongly suggests that antipersonnel effects were so minimal as to not be worth mentioning.

Regards,

John Kettler

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Originally posted by Jeff Duquette:

</font><blockquote>quote:</font><hr />Originally posted by Stalin's Organist:

4 F-86A's experimentally armed with 20mm cannon were trialed in January 1953 and 282 combat missions flown - see Joe Baughers F-86 page

Interesting. Well I stand corrected. Thnx for the link. I didnt look too closely, but were any of these F-86 involved in air-to-air combat -- any confirmed air to air kills? </font>
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Thnx Stalin. Sorry -- don't wanna continue off into la-la land relative to the thread topic, but the page also goes on to say:

"The combat tests were sufficiently encouraging that the T-160 cannon was placed into production by a division of the Ford Motor Company as the M-39, and the cannon ended up arming the F-86H and some of the Century Series of supersonic fighters."

I thought I read something once about Mig cannon fire being considered to be pretty destructive relative to 50-caliber fire. But I may be thinking of something else

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Mig cannon fire was certainly very destructive - the 2 x 23mm cannon were appreciably more powerful than 20mm cannon and the 37 could blow any aircraft out of the sky with a single hit - the armament combination was designed to shoot down bombers, which it did very well and forced an end to daylight bombing of Nth Korea.

However the cannon were very slow firing compared to 6 x .50 cal's, so arguably not so useful vs small, fast-moving fighters.

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Originally posted by Stalin's Organist:

Mig cannon fire was certainly very destructive - the 2 x 23mm cannon were appreciably more powerful than 20mm cannon and the 37 could blow any aircraft out of the sky with a single hit - the armament combination was designed to shoot down bombers, which it did very well and forced an end to daylight bombing of Nth Korea.

However the cannon were very slow firing compared to 6 x .50 cal's, so arguably not so useful vs small, fast-moving fighters.

Sounds like your pretty up to speed on this ****. You do flight sim games as well as Combat Mission?

I'm not very hep on cannon load-outs for aircraft. Did the Korean War Migs use a mixture of ammo types for their cannons? OZT and BZ. Or did they pretty much use only BZ if dog fighting was anticipated?

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i've no idea about their ammo loads sorry - but I imagine it's probably on the 'net somewhere.

I'm jsut an enthusiastic amateur - I dont' play flight sim's - I'm more interested in the technical aspects adn the strategic campaigns.

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here we go. this is the mkIV spaced armor I was thinking of. these are from photos i took at aberdeen a couple of years back. most of the mile of tanks near the entry gate have been restored to this sort of condition. pretty nice. even gotz' an Afrika Korps palm on the thing.

img04jo4.th.jpg

img09zu5.th.jpg

and Crisp’s Stuart ;) -- that's my finger on the second photo doing a highly calibrated measurement of the frontal armor thickness.

img19at5.th.jpg

img26re1.th.jpg

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Jeff Duquette,

Nice shots! I think that is the Zusat (something or other) I was reading about. Am guessing that these pieces are the face hardened plates that pretty much nullified the 2 pdr. AP shot.

On a slightly different note, what did you think about the info on the airburst capability for German 2 cm cannon on the Panzer II and other AFVs?

Regards,

John Kettler

[ January 29, 2007, 01:05 AM: Message edited by: John Kettler ]

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A little basic physics for the metaphor reasoners, along with a few noteworthy facts. The total energy is the thing. And tiny HE burster charges just can't carry enough of it to the target.

One fellow cited the APHE charge size in a 3 inch gun. Yeah, that could get to 65 grams or so. A charge of 65 grams releases approximately 282,000 joules. But then, a 3 inch shell leaves the muzzle with a kinetic energy 7.7 times that figure.

Meanwhile, the bursting charge in a German 37mm APHE round was a whopping 13 grams, instead. Meaning its total energy released is about 50,000 joules. The kinetic energy is only 190,000, but still 4 times as large. (The 2 pdr gets 282,000 with solid shot, from a heavier projectile and marginally higher velocity).

Carrying the high explosive all the way to the other end of the engagement is a finicky roundabout way to get more total energy. Just burning the extra powder in the tube will do as much.

Oh and the 37mm did have some bursters as large as 26 grams - for "high explosive". (lol). (The US 37 have 39 grams, and a later German type reach 45 - but all for pure HE, not APHE).

HE bursters are largely superfluous for very high energy guns, which hit with 5-10 million joule force and upward regardless. And not enough can be carried to help appreciably for small caliber ones. Middling guns might be marginally more useful for the extra energy - but nothing compared to e.g. going up to 50L60 from 50L42 and burning a longer powder case in the firing tube.

(If anyone is having trouble groking that total energy is the thing, ask yourself where the kinetic energy goes. Bits of flying metal are made either way...)

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It’s been suggested that 2-pdr AP-shell was considered no more effective than 2-pdr AP-shot in generating behind armor effects. This is based on a quote from Hogg’s book on US and British Artillery. The Hogg quote is at odds British field trials briefly discussed by Jentz in his book on Tank Combat in North Africa. Be that as it may.

Hogg’s take on 2-pdr AP-shell has been used as an example to demonstrate that other small caliber projectiles must be equally ineffective in generating behind armor effects. There isn’t anything wrong with using this logic, however additional information – to include the Jentz quote – has been presented to suggest that AP-shell might be more effective than is being argued. In addition, and more specifically 37mm pzgr might not be directly comparable to Hogg’s take on the 2-pdr AP-Shell. To recap:

1) Small caliber bursting charges can in fact generate effective fragmentation. Even 20mm projectiles with small bursting charges can generate in excess of 100 effective fragments. If a projectile by bursting can throw additional fragmentation into a crew compartment in addition to whatever fragmentation is developed during plate perforation why would it not be more effective than solid shot?

2) All other major producers of tank fired AP projectiles during WWII employed various forms of AP-Shell. These other producers appeared to have thought that a bursting charge would enhance behind armor effects. This to include the USA, Russia, Germany, and Italy. Lesser known producers of AP-HE (large and small calibers) for tank and anti-tank fired projectiles included the Czechs and the Poles (there are probably more on this list, but I am sticking to information I have seen). These AP-HE shells ranged in caliber from 20mm to 128mm.

3) The British – aside from the already mentioned early versions of 2-pdr AP-Shell (and 3-pdr APHE) – did not use bursting charges in any of their tank fired AP projectiles. To elaborate a bit, in my mind there is no direct correlation between the fact that the British didn’t use a bursting charge in 2-pdr and all small caliber AP-Shells bursting charges being ineffective. This argument misses the fact that no British tank fired AP during WWII used bursting charges. So by this same logic we might conclude bursting charges for both small and large caliber projectiles were ineffective – all because the British didn’t use bursting charges in any of their tank fired AP projectiles. One would therefore have to ask where the cross over point is. 2-pdr and 37mm to 47mm(?) calibers; 6-pdr and 50mm to 57mmcalibers(?); 17-pdr and all 76mm to 85mm caliber(?) , 20-pdr/ 90mm to 128mm(?). Or does this argument extend further up the food chain – were the bursting charges in 14-inch APC, 15-inch APC and 16-inch APC also ineffective at enhancing behind armor effects?

4) The 2-pdr AP-shell referred to by Hogg is of course not German 37mm pzgr. The contrasts between 2-pdr AP-HE and 37mm AP-HE include what appears to be a larger bursting charge within the 37mm pzgr. In addition, the explosive filler utilized in the two projectile differs. 37mm pzgr uses a much more modern and more powerful explosive than the 2-pdr AP-HE shell. PETN in the 37mm pzgr vs. Picric Acid in the 2-pdr MkI APHE shell. The level of fragmentation generated by a bursting charge is correlated to the power of the explosive used in the bursting charge (see attached).

The attached figure represents testing data from the US Army’s Material Testing Laboratory – circa 1950’s thru 1960’s. Sorry -- no fragmentation data for picric acid as the US had deemed this particular explosive unsuitable for use in High Explosive bursting charges even before their entry into WWII. Extrapolation of this data (fragmentation as a function of explosive power) suggests that based upon bursting charge material (i.e. Lyddite at about 100% and PETN at about 166%) we could expect about a 50 to 60% increase in fragmentation for the PETN charge over Picric Acid. But of course it is better than this (or worse depending upon your perspective). The 37mm pzgr bursting charge appears to be bigger than 2-pdr AP-HE, and of course fragmentation is also proportional to the size or weight of the bursting charge.

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

2-pdr AP-HE also generates “X” number of fragments during perforation and in addition it generates “Y” number of fragments by the bursting charge. It’s behind armor fragmentation is therefore:

= X + Y

37mm pzgr AP-HE also generates “X” number of fragments during perforation, but it generates 1.5 to 1.6 times Y 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).

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

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

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

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

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

2pdr APHE introduces 100 + 100 = 200 effective fragments into the crew compartment

37mm pzgr APHE introduces 100 + (1.5 x 100) = 250 effective fragments into the crew compartment

Ok – quiz time:

If you wish to maximize kill probability against a tank from projectile penetration, does it make more sense to:

a) Introduce 100 fragments into the crew compartment; or

B) Introduce 200 effective fragments into the crew compartment; or

c) Introduce 250 effective fragments into the crew compartment.

fragmentationvsburstingnm7.th.jpg

[ January 29, 2007, 12:42 PM: Message edited by: Jeff Duquette ]

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Your quiz is a strawman because it misses - or ignores - something that Jason alluded to. A solid shot (AP) is heavier than a shell, therefore it carries more KE with it into the target - much more if it is also given a higher MV because it doesn't have any thin walls or fragile fuzes.

On the other hand, a shell (APHE) carries some PE with it in terms of the stored energy in the burster.

APHE can only be 'better' than AP if the gain in PE is greater than the loss of KE, whilst retaining enough KE to penetrate in the first place.

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