Jeff Duquette

Hey John K: Some of what you maybe recalling might have been from your readings in Jentz. There is a reference by Jentz to G/B Jerratt (I have included it with the other scanned material below). Best Regards Jeff From: Thomas Jentz “Tank Combat in North Africa, The Opening Rounds”. Schiffer Publishing Limited, 1998 From Page-44 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 pro¬jectile 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. From Pages 46-47 4.1.1.2 EFFECT AFTER PENETRATION The destructive effect of the 2-pounder AP-Shot after penetration was based solely on whatever kinetic energy re¬mained in the solid shot, shot fragments if it shattered, and/or fragments of armor plate broken off by the hit. Starting with the design of the Pz.Kpfw.l, German designers had taken extra precautions to reduce the probability of fire as a result of penetration. Fuel tanks were separated from the crew com¬partment by a firewall (about 5 mm thick). In the case of the Pz.Kpfw.ll, the fuel tank, located on the right side of the crew i compartment, was isolated by 8 mm thick armor plate. As a further precaution, the main gun ammunition in the Pz.Kpfw.lll and IV was stowed in bins whose sides were 4 to 6 mm thick. In addition, main gun ammunition in the Pz.Kpfw.lll and IV was stored low in the hull. Thus, even when a 2-pounder AP-Shot managed to penetrate through the armor, it needed suf¬ficient residual kinetic energy to penetrate the firewall or am¬munition bins in order to destroy the tank by setting it on fire. Penetration of a Pz.Kpfw.lll or IV by 2-pounder AP-Shot fired at 600 to 1500 yards range frequently resulted in crew mem¬bers being wounded but infrequently resulted in destruction of the tank by causing irreparable damage or by setting it on fire. Of those Pz.Kpfw.lll and IV knocked out in combat by AP-Shot, fewer than 20 percent were destroyed by fire or damaged so severely that they couldn't be repaired. ==================================== Below is Jentz discussing German AP-HE projectiles – from pages 48-49. ==================================== As stated in a German report on armor-penetration curves: Basically all penetration data are valid for projectiles of good quality. The estimate of penetration for "worst" pro¬jectiles is possible only with great difficulty. The penetration can spread over a very large range below the given value. The regulations for acceptance of projectiles stipulate that a certain number of projectiles (1/2%) will be presented for in¬spection. Two-thirds of the projectiles which have been fired against armor plate, must satisfy the given conditions. Based on past experience, it can be stated that the largest part of the deliveries satisfy these conditions. 100% assurance is not given; it may always be expected that a small percentage do not achieve the specified penetrating ability, because of shattering prematurely. Also the explosive charge in these shattered projectiles will not detonate. The effect of the projectile inside the tank and the prob¬ability of hitting the target are not considered in these graphi¬cal charts; thus only the complete penetration with the to¬tal effect inside the tank is considered. As a rule, this ef¬fect is of annihilating power when using armor-piercing shells with a high-explosive charge. When using hard core projec¬tiles, steel or soft iron core projectiles, or hollow-charge pro¬jectiles, completely annihilating effect cannot always be ex¬pected with a single shot, because the crew, located in the dead space of the tank, cannot be hit under certain condi¬tions. A limited effect, without piercing the tank by the pro¬jectile (effect produced by back-spalling of armor plate and punching holes (Stanzpfropfen) is frequently achieved with plates that are about 10% thicker than the thickness presented in the graphs. AND from page 54 4.1.2.2 EFFECT AFTER PENETRATION In all calibers of 3.7 cm and above, the normal armor-piercing round designed by the Germans contained a high explosive filler with a delay fuze. Penetration of a British tank by a German armor-piercing shell frequently resulted in crew members being wounded as well as destruction of the tank by causing irreparable damage or by setting it on fire. Not until 1942 did the British investigate the cause of fires in the tanks and began to install armored bins to protect the ammu¬nition. As recorded by Major G/B. Jarrett in May 1942: The German projectiles which have caused the greatest amount of damage to Allied tanks in the Western Desert campaigns have been the A. P. -H. E. type in 47 mm, 50 mm, 75 mm and 88 mm respectively. These projectiles at long ranges need only attain a partial penetration and the explosive charge can com¬plete the destruction of at least the tank crew. At closer ranges the destructive effect is very great, where in many cases de¬struction of the tank is permanent. When the 7.5 cm K.Gr.rot Pz. was fitted to an American casing and fired from the 75 mm M2 gun, in May 1942 Lt.Col. Gruver reported: Each German AP-HE round fired may safely be presumed to have put the tank out of action. In this con¬nection it was noted that the fuze functioned perfectly, that is to say it functioned only after penetration and then always in the fighting compartment where the most damage is done. Parts also frequently penetrated into the engine compartment. The destructive effect of the Pzgr.40 after penetration was based solely on whatever kinetic energy remained in shot fragments when it shattered and/or fragments of armor plate broken off by the hit. Jentz Refering to Italian AP-HE, page-57 4.1.3.2 EFFECT AFTER PENETRATION The Italian 47 mm armor-piercing round contained a high explosive filler with a delay fuze. Penetration of a British tank by a 47 mm Italian armor piercing shell frequently resulted in crew members being wounded as well as destruction of the tank by causing irreparable damage or by setting it on fire.

75mm M72 AP [ January 22, 2007, 10:33 PM: Message edited by: Jeff Duquette ]

The ability to produce a base fuze is of course not my question, nor is it what I said. Obviously the British were producing base fuzes for a wide range of APHE calibers long before WWII ever hit the front page news. But than base fuze and bursting charge problems associated with armor piercing shells also stretches back some number of years. For example, I think Campbell credits RN shell hits at Jutland with perhaps one (perhaps it was two?) bursting charges that actually functioned properly following perforation (See: "Jutland An Analysis of the Fighting"). My point in going back to WWI is only that the ability to produce a base fuze says nothing about whether or not the device was capable of functioning properly. Even the Germans – in post WWII tid bits that can be found in the BIOS report on German Tank Armor – imply problems with their own AP-HE bursting charges functioning properly all of the time. My question is more specific to source material regarding side-by-side testing of behind armor effects of 2pdr solid shot and 2pdr APHE. You indicated in one of your posts above: “Trials with the 2-pdr found not a ha'porth of difference between AP and APHE rounds, so the APHE was never ordered into full production.” I’m not disagreeing with you (nor am I agreeing with you for that matter). I’m simply interested in a cite for the original report\reports that detail the effectiveness of solid 2-pdr AP vs. 2-pdr AP-HE. Can this be found in a WO report? If so do you by chance have the number\numbers? Best Regards JD

Interesting disscussion. I'd be interested in the source or a cite for side-by side testing reports conducted during this period for behind armor (armour) effects of solid shot vs. APHE. I know the British were not so keen on APHE, but was this a function of developing a reliable base fuze?

I think you mean the sloping armor on NKPA T34/85s – or your finger hit the five key instead of the three key. Some of this was apparently traceable to ricochet. Some of it was attributable to old bazooka ammunition as well as fuzing issues. In addition, the shaped charge cone in the old bazooka projectile had a tendency to dislodge itself from its explosive. The projectile sometimes functioned more like a pseudo-HESH round than a shaped charge. The cone could be found afterward wadded up in baseball sized blobs. No jet action what so ever. This was apparently addressed with the M20 super bazooka which is said to have had very good success against NKPA T34/85’s. As I recall the Marines had occasion to use the M20 on a number of occasions vs. T34/85’s during their push through Inchon and Seoul. Any projectile is going to have some ricochet potential -- depending on impact velocity, angle of attack and hardness of the target. The armor on the T34/85 was very hard. HHA like 350 to 400 BHN, and it was highly sloping. I also have photos USMC trials of 90mm HEAT, and 90mm APBC that ricocheted from the glacis of an M48. Much softer cast armor, but highly sloping. I think highly sloping armor can present problems with fuzing of HEAT rounds. I don’t know enough about fuzes to know why this is. But as I recall shoulder fuzes, in addition to the standard end of probe fuzes, were added to latter models of 105mm and 120mm HEAT – ala M456 and M830. Or maybe the M830 always had a shoulder fuze and probe fuze based upon experiences with the M456 – can’t recall the exact sequence of design changes. Best Regards JD

Hi John: Once again I completely agree with your logic. I'll actually go even further to support your logic and say that the field manual for TOW specifically states 2B shouldn't be employed for anything other than armored targets. The layout of the EFP warheads and it's megnetic fuzing suggest that it would be relatively ineffective against buildings, bunkers, etc -- MOUT type targets. 2A -- or better yet the new bunker buster TOW would be the missile of choice in such scenarios. But you know how it goes sometimes. Someone gets it in their mind that 2B is somehow like BILL-2 or some such thing. Anyway, it's not that critical. Thanks again for your efforts Best Regards Jeff

Hi John: I thought of that. I've actually had good luck with this approach in the past when researching various weapon systems -- nothing classified mind you. However, Raytheon has a little blurb on there web site that basically says they won't respond to questions from researchers. I suppose I'll give it a whirl anyway -- all they can do is say they dont answer questions from folks conducting research on their products. "Read Our Web Site Notice Dumbass" -- or something to that effect. Regards JD

Thnx John. I thought my questions might be long shots. But it never hurts to ask. I've read all of the Raytheon material as well as most internet net based public domain poop. I agree about the impact fuze bit, but of course am always looking for proof positive on it as well as export information and/or foreign manufacturing rights for the 2B. All the best JD

Thnx Steve. Looking forward to seeing what you folks come up with for the new game.

John: Do you still have contacts at Hughes? I had a couple of questions regarding TOW-2B. What countries has the United States sold 2B, and what – if any -- foreign manufacturers are licensed to produce TOW-2B. The Swiss and Italians used to produce older editions of TOW. The UK have been producing FITOW. However, out-of-country 2B production is difficult to trace. Lastly -- and this is a little more obscure -- but I have been curious as to whether or not 2B has any sort of impact fuze in addition to its magnetic sensor and laser. In other words, can it be employed against non-armored targets -- bunkers, buildings and the like. I’m thinking no. The additional capability makes little sense to me considering the EFP warhead arrangement – aside from the perspective of the missile having duel purpose capability. But I don’t know for certain. Lack of any sort of impact fuzing; or the presense of an impact fuze would put the question to rest. Regards JD

Hi John: TOW-2B RF is wireless. Wireless TOW-2B has been successfully demonstrated, but apparently requires further development before full blown production -- this as of 2003. I have not seen any news of the 2B RF in production as yet, so I assume it is still being tested. TOW-2B (wire-guided) is "fly-over shoot-down". Target picture is the same for the gunner as with other TOW missiles -- he just keeps his cross-hair center of mass. As the missile approaches the intended tank target the missile is designed to fly above the LOS to the target by about 2.5m. The triggering mechanisim consists of some sort of magnetic signature recognition by the missile of the tank. When the missile is overhead it fires two tantalum EFPs down through the top of the tank. It is a bit like BILL-2, however BILL-2 is of course shorter ranged, and relies on two shaped charge warheads rather than the EFPs of TOW-2B. Best Regards Jeff

I did a bit of additional digging into some of the details regarding common protection standards used in body armor testing – ala NIJ. The 7.62x39mm (Ball) is rated as a lower level of threat than NATO 7.62x51mm (Ball). The 7.62x39mm can be defeated by a 7.62x51mm NATO Ballistic Standard Product. In other words, 7.62x39mm Ball would typically be defeated by NIJ Level-III Armor.

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double post [ July 28, 2006, 06:56 AM: Message edited by: Jeff Duquette ]

There are a number of ballistic protection standards for body armor. NIJ is typically employed by producers of body armor utilized by law enforcement folks in the USA. It is one of the easier standards to research as it is all public domain. Protection against 7.62mm NATO FMJ equates to Level-III armor under NIJ Standards. Protection from .30-caliber Armor Piercing equates to Level-IV armor protection. Level-III and Level-IV protection typically involves upgrading a Level-II or Level-IIIA aramid fiber or polyethylene fiber vest by inserting plates made from either: ceramics, high hardness steel, or polyethylene into various pouches on the vest. Under NIJ standards Level-III protection has to withstand six hits per armor part from 7.62mm NATO FMJ at an impact velocity of 847m/s. Basically point blank range. No penetration or spalling is allowed from either the armor or bullet. In addition there is a maximum allowable back surface indentation (back surface signature) that can not be exceeded. This is the blunt trauma requirement for the vest. Under NIJ Standards, BSS can not exceed 44mm into a layer of ballistic clay placed directly behind the vest. NIJ Level-IV protection is such that each armor part must withstand one hit by .30-caliber M2 Armor Piercing Bullet with an impact velocity of 878m/s. Again this equates to point blank for the M2 AP round. No allowable bullet fragmentation\spall or armor fragment or spall can pass through the armor. Same blunt trauma indentation requirements as Level-III armor. Spall and fragmentation testing is done in a similar fashion to protection ballistic limit P(BL) – i.e. a thin foil is placed behind the armor. The foil can’t be perforated by fragments or spall. MIL-SPEC body armor is of course subject to its own standards and specifications above and beyond NIJ. The most obvious difference being fragmentation protection testing. The armor is tested against FSP in addition to the standard realm of small arms projectiles. It would appear from various recent headline stories that manufacturers of body armor for Law Enforcement use have tried to jump into armor production for military use and have been somewhat stymied by Military testing standards. [ July 27, 2006, 08:29 PM: Message edited by: Jeff Duquette ]

Hi John: APFSDS will ricochet like any other projectile – given the right conditions. Mostly this means very high obliquity attack angles. The probability of ricochet is increased or decreased by other factors such as impact velocity and the material properties of both the rod and target. Harder armor makes the likelihood of ricochet greater. Rod density and rod strength also play a part. Off-angle shots combined with inherent armor plate slope will also increase the likelihood of ricochet – compound impact angles. Lower striking velocity also increase the likelihood of a rod penetrator ricocheting. LRPs constructed from steel – ala the BM-1, or BM-2 or BM-6 are more likely to ricochet than WHA or DU LRPs. Aspect ratio of the penetrator will also influence the critical ricochet angle. Higher aspect ratios have higher critical ricochet angles. Modern WHA and DU rods you are looking at critical ricochet angles in excess of 70 to 80 degrees – again depending upon the above variables. Long rod penetrator ricochet actually results in the formation of a plastic hinge within the rod. As the rod begins to redirect into a rebounded trajectory, the rod bends along the contact area between rod and plate. A plastic hinge forms and propagates along the length of the rods from tip to tail as the rods direction is turned away from the surface of the target. So – yes the rod is subject to a large amount of stress and plastic deformation; fracturing of the rod into multiple segments can also occur. As to the shot trap on an Abrams – I think the gap between the bottom of the turret and the glacis is required – at least partly so – to allow the turret to traverse completely around the hull. The rear deck is raised considerably above the elevation of the glacis, so this gap actually becomes pretty tight between the front of the turret and the rear deck. Vision blocks and the drivers hatch also come into play. The frontal turret area that overhangs the glacis – as stated earlier -- is pretty much all part of the special armor package. Layers of steel, DU and ceramic by most accounts. Assuming a rod penetrator did ricochet off the highly sloping glacis of the Abrams, it is quite likely that the redirected trajectory of the rod would put the new impact location into the bottom of the special armor package – at a very awkward angle of attack for the rod. The rod may well be fractured\fragments after the ricochet. It would certainly strike the bottom of the turret armor at a lower energy state following the ricochet. However, given the right ricochet conditions it does not seem unrealistic to think that a rod penetrator could ricochet from the glacis and strike a very vulnerable area between the turret and hull. The probability seems low -- but it could happen. I won’t attempt to defend or prove any of the above. I am simply regurgitating what I have learned from studying the subject of long rod penetrator ricochet. A number of studies were conducted by A. Tate on the subject of long rod penetrator ricochet. These papers are a good place to start any additional reading on the subject. Regards JD [ July 10, 2006, 08:27 PM: Message edited by: Jeff Duquette ]

I see. I am familiar with this paper, although I will admit I had only skimmed parts of it sometime ago. So your interest is not in modeling long rod penetration? There are -- as you may already be aware -- a number of DTD papers written on shatter. Have you looked at W-172-8a "The Shatter Effect"? I have no idea what the PRO cite may be on this one as a copy of it made it's way into American Archives and eventually into my hands via this circuitous route. 2-pdr and 6-pdr AP & APCBC shatter issues. As I recall the conclusion from this paticular study boiled down to higher t/d ratios combined with high obliquity angles of attack, and near muzzle shots – i.e. higher projectile velocities. Course this was all empirical. Do a bunch of shoots and find out what conditions resulted in perforation and what conditions resulted in shatter. Nothing detailed about the mechanics of what may have been causing shatter – aside from various brain-storms and guesses.

Regarding adiabatic shear banding – is someone here trying to determine why DU rods penetrate more RHA than WHA rods?

On the first bit regarding WO 291/1330 – no idea why it says 0.74. Again, it is simple enough to verify yourself that this is in error. Determine the area under a normal distribution curve. My guess is that the original typist put in “0.74” instead of “0.674”…i.e. He or She accidentally dropped the “6” while merrily banging away at 65 words per minute. Shot-to-shot dispersion is an inherent or systematic error. It can’t be corrected by training your gunners more rigorously; or making sure you conduct your routine maintenance; or from sight & gun calibration; etc. Jump on the other hand is a well recognized constant error that is correctable. Calibration via zeroing is one way to correct for jump. The most modern MBTs account for jump via correction factors input into their CEU. These can be either fleet specific averages or they can be individual corrections determined for the specific foibles of a given tube via sight zeroing. Obviously P(h) is a function of more than inherent shot dispersion – wind, cant, parallax propellant temp, biorhythms of the TC and/or gunner on that particular day, etc etc. Many of these are automatically compensated for by the FCS of some modern MBTs. I look at it more from the perspective of how the MPI differs from the where the gunners aim point happens to be. Inherent shot spread follows the MPI about and radiates from that point. It doesn’t necessarily follow the gunner’s aiming point about. For example if the TC over estimates range to target, the gunner will still aim center of visible mass, however the MPI will be above the aim point some distance dependent upon the magnitude of the ranging error. It is still conceivable that the projectile will strike precisely where the gunner has aimed due to inherent shot-to-shot dispersion – and luck. But obviously the greatest P(h) will occur when the MPI and aiming point are coincident.

Sorry. One more question. You said you were employing "Applied operations research: Examples from defence assessment", by R W Shephard et al. Which excercise are you refering to? #5?

The 50% Zone is +/-0.67449σ. Run your Z-values. +/-1σ would imply you are referring to an ~68.27% Zone. I am referring to shot-to-shot dispersion -- systematic error related to the ammunition. As to what you are referring to with “muzzle dispersion”, well I am still confused as to what it is supposed to represent and how you developed this number. It’s not really nomenclature I have seen before. Is this your own term? Perhaps you can walk me through an example of how you determined this value so I have an idea as to what it is you are talking about. As to the numbers I have posted seeming too small – well I can’t help that -- they are what they are. The 50% zones for 88mmL56 firing pzgr. were 0.4-mils in height & 0.2-mils in width at 1000m. A pretty far piece from 1-mil, and this was crica-1940’s technology.

Firing tables (range tables for you UK folks) are the best source. Don't know about early Soviet APFSDS aside from 100mm BM1 & BM2. But than no Soviet tank was sporting a 125mm smooth-bore in 1962. As to NATO guns of 1962 vintage, nobody in NATO had an in service APFSDS round at that time. The closest thing would be APDS. The 50% Zone for 105mm L7 gun firing L28A1 APDS (or the M68 gun firing M392A1) was 0.24-mils in height and width\breadth. See War Office Publication dated 5th October 1960, "Range Table for Gun, 105mm Tk. L7A1, Shot, 105mm APDS". I suppose I would need to understand what you are referring to by "muzzle dispersion". Usually shot-to-shot dispersion is presented in terms of probable error or dispersion probability zones –Like a 50% Zone, or 90% Zone. When you say "muzzle dispersion", are you talking about shot-to-shot systematic dispersion? In addition, when you say 1-mil of "muzzle dispersion" are you intending this figure to represent a specific dispersion probability zone? Regards JD

Hi John: Inherent dispersion for most NATO APFSDS typically runs around 0.2mils in both the vertical and horizontal planes. This is only shot-to-shot dispersion. Best Regards JDuquette

Very cool! Hey -- what grass mod are you using?

While at the Littlefield Armor Collection I took angular measurements of the Panthers glacis and upper side hull plates using a dial protractor – the kind with the magnetic base strip. The tank was on blocks as it was being refurbished. The engine was not in the hull, nor was the turret on the hull. I first took several shots on the hull deck and found it to be perfectly level. I also measured the concrete slab in several locations to make sure that the Panther was setting on level ground (or should I say the timber blocks were setting on level ground). The floor was also perfectly level. I found that the glacis was inclined at a tad over 57-deg – perhaps 57.3-deg. Measurement of the upper side hull plates came out to pretty much right at 30-degs. Sort of interesting. I took a photo of this little exercise as I felt sure most folks would be skeptical. Obviously when the engine and turret were installed the "relative" glacis inclination would change slightly. But given manufacturing tolerances it would seem odd if every Panthers glacis sat perfectly at 55-degrees. I plan on heading back when refurbishing is complete, and will take additional angular measurements when the vehicle is setting in a natural position.