Thursday, 20 October 2016

7.5 cm Sprenggranate 34

Much talk is dedicated to various armour piercing munitions, but high explosive shells are no less important for cannons. Let's take a look at the data sheet for high explosive ammunition of a 7.5 cm KwK 40 L/43 gun.

"Spreng-Granate 34. Vo = 550 m/s

Without delay (o.V.): use against strongpoints, AT guns and riflemen, masses of targets, against tanks use only with impact fuse.
With delay: (m.V.): use against targets behind cover, or, as an exception, against live targets with ricochet.

Shrapnel effectiveness area:
  • At an impact angle of less than 45°:
    • Each side: 15 m
    • Forward: 7 m
  • At an impact angle of over 45°:
    • Each side: 18 m
    • Forward: 10 m
  • From a ricochet, at a height of 10 meters:
    • Each side: 10 m
    • Forward: 8 m"

While standards of "shrapnel effectiveness" vary between nations, a quick comparison with Soviet 76 mm HE demonstrates the superior effectiveness of the latter (assuming the PzIV isn't firing from a ramp to make its shells land at a sharp angle). 


  1. The sources referenced doesn´t demonstrate a "superior" effectiveness for the one or the other. All data are simplified and do not show the fragment pattern but a simplified box.

    The soviet data give max. extansion of the boxes outer rectangle while the german data give the distance from the center of the box to one edge. A just comparison of the numbers is therefore apples and oranges.

    Further, the definition of what is considered as "effective boundary" is unknown and it does not follow that both, german and soviet follow the same standarts in determining what exactly consitutes effective fragmentation.

    The 75mm fragmentation pattern diagram, which I have in my collection, gives the following information:

    boundary definition: 98.4% probability to have >0.5 fragments at each square meter, burst at ground level.

    side lobe pattern: 12.0m at height of burst, 36.0m at 6.0m in front of burst point, and max. 56.0m at 20.0m in front of burst.
    Max depth of pattern with >1 fragment per m^2: 38.0m

    1. Your knee-jerking would be amusing if it wasn't so predictable. Quick look at hard numbers readily available online peg the SprGr 34 as both lighter overall (5.75 kg to 6.2 or more) and having a smaller explosive charge (0.66 kg to 0.71+) than the Soviet and US equivalents - in other words, less of both metal and explosive to make fireworks and fragments with.

      Get that stick out of your ass already.

      This is, incidentally, not terribly surprising; the German gun (or rather its towed original) was designed from the ground up as an antitank weapon whereas the rivals had their roots in field guns (the classic French "soixante-quinze" in the case of the US 75 mm), for which HE performance was obviously a far higher priority from the start.

  2. Give it a try to comprehend before acting out and get Your facts straight. The author of this article incorrectly claimed "superiority" of the soviet 76.2mm by dragging out an apples vs oranges type comparison of two different fragmentation pattern data using different references. For establishing a superiority, I´d expect at least to see a 1/3 advantage based upon the same measuring methodology.

    A sober investigation instead tells me that there was little to choose from in HE-effect of the high explosive projectiles between german 75mm, US 75mm and SU 76.2mm and that any "superiority" of the Soviet 3" HE projectiles as used in tank guns disappears. In fact, only the british 17pdr and US 3" fall short, because they are significantly inferior in this regard:

    The original german 75mm Spgr.Patr. 34 uses 660g TNT (fired from L24 howitzers), which was replaced by higher density Amatol with 680g. filler weight the german 75mm spgr.Patr. 34(KWK) and Spgr.Patr. 42 (KWK 42).

    680g Amatol for the 75mm compares unfavourably with what exactly(?):

    The US 75mm HE M48 uses 764g TNT (1 lbs 11 oz)
    The soviet 76.2mm UO-353M used 627g Amatol
    The soviet 76.2mm UO-355A uses 710g of TNT
    The soviet 76.2mm UF-353 uses 816g of TNT
    The US 76.2mm HE has only 255g of TNT (9 oz)
    The UK 17pdr (3") has only 482g TNT (1 lbs, 1 oz)

    Considering that TNT is less powerful ounce by ounce than amatol, which was replacing TNT on account of it´s substantially higher chalorific value, it does not follow conclusively that the 75mm HE is appreciably inferior in HE effect to an UF-353 and probably has more power aviable than a 76.2mm OU-353M and OU-355AM.
    The US 75mm, soviet 76mm and german 75mm are all very powerful HE projectiles.
    If anything, it may be claimed that the US 3" and UK 17pdr HE are significantly inferior to the other three in this regard. The german 75mm was deadly against both, hard and soft targets.

    For a reasonable case of the quantification of fragment pattern on account of the US 3" M48 example see here:

    1. The feebleness of the US 76 mm HE shell is well known (and was one of the major pieces de resistance against the adoption of the gun), which is why I didn't even bother bringing it up. And as I understand the Brits persisted with their peculiar habit of essentially plain not supplying even poor HE to their antitanks guns, even if such shells had been designed, so the same applies.

      Technical nitpickery: looking at the REF table on Wikipedia, Amatol is actually *less* dense than pure TNT - 1.5-1.55 g/ml (depending on mixture) to 1.6. And at the higher ammonium nitrate contents it's actually LESS powerful - the table gives REF of 0.91 for the 50/50 mix. (80/20 is 1.10.)

      The point of the higher ammonium nitrate mixtures is of course to stretch supplies of the more expensive and difficult to manufacture TNT further. Just sayin'.

  3. Technically, the information in regard to Amatol in wikipedia is incorrect. Actual data for TNT and Amatol 60/40, respectively:

    TNT (FP C/02) in pressed blocks: 1.58
    Amatol (poured): 1.60

    chalorific value:
    TNT: 840 kcal/kg (1330 kcal/dm^3)
    Amatol: 900 kcal/kg (1440 kcal/ dm^3)

    gas production:
    TNT: 800 l/kg
    Amatol: 790 l/kg

    pressure wave:
    TNT: 1.0 (reference)
    Amatol: 1.10 to 1.36

    Source: Table provided by the Chem.Physik.Versuchsanstalt Kiel to NAVTECMISEUR 1946, orginally classified SECRET.

    1. Literally every number I can find for TNT density reads as 1.654 g/cm^3, so you'll have to excuse me if I take the modern numbers over some seventy-year old paper thanks.

      Oh, and that US test document you linked earlier? I ran into a link to it while doing a quick Google on the topic:

    2. Also relevant:

      I'll be the first to admit most of the data in the tables might as well be Sanskrit for all I understand of it, but even a layman can grasp the "Fragmentation text" numbers and the velocities for the blast waves.

  4. The numbers come from the institution in charge in Germany during ww2 for explosive research and for creating the specifications of explosive fillings in warheads and projectiles. Do You think it is a stretch that we can infer from this that they knew less about their explosives than anybody else?

    1. Modern instruments > 1940s instruments. Also not sure if that number is even "density" in the everyday weight per volume meaning and not some more obscure context-specific measure. That '71 US military handbook linked above certainly has a separate figure for "density" in the "Detonation rate" box...

    2. Ohh now I get where the discrepancy comes from. TNT is 1.654 g/ml in its base crystalline state, but less dense in the cast (1.58-1.59 according to the manual above) or pressed (depends on the pressures used) forms that actually go into shells and such.

    3. Do they have info on 40/60 ratio Amatol? The US ordnance information all have H.E Projectile, Type 34, 75-mm listed as using 40/60 ratios (and I've checked other rounds to make sure they weren't using AN/TNT ratios for some reason). Of course that could just be bias due to whatever samples they had (possibly the ratio was further diluted as the chemical manufacturing problems became worse in the later years of the war). The version supplied for the Geb G.36 mountain gun are listed as 90/10 TNT/Amatol mixtures.

    4. *shrug* Amatols are pages 20-26 in the PDF. They have 80/20, 60/40 and 50/50 (AN/TNT) in the tables - those being the most used ones if I understood correctly.

  5. To presume that it wasn´t possible to determine a g precise measurement with 1940 instruments is a very bold presumption. Even fractions of a g could be precisely determined at three digit resolution since the 20´s in every pharmacy, let alone a fully equipped lab dedicated for explosive research. I am surprised to see such nonsensical idea relied upon here.

    TNT desensitizated in beewax and pressed into blocks -as in case of the older Fp C/02 filling had in fact a lower density than Amatol. Notice also that the projectile´s cavity was the same in terms of volume. 660g TNT fitted in the same cavity as 680g Amatol.
    Amatol produced slightly less gas volume but elevated the overcompressed gas bubble to higher energy due to it´s higher chalorefic exposure. Thus, lending more energy to the products of blast and overcompression.

    While a comparison is not possible to the Soviet 76.2mm shell, a comparison is possible to the US 75mm M48 due to the excellent data provided by Tolchs experimental studies of 1938 vintage (the 75mm T3 M48 shells used by him contained 707g / 1.56 lbs TNT).

    In static explosion, the 1.0 fragment probability border* was approached at 18.2yds, which equates 16.6m in front of the shell.
    For the 75mm Spgr.Patr.42 this limit was far further, at 38.0m in front of the shell (= 41.5yds)
    The max. sidelobe for 1.0 probability* for the M48 was 21 yds one direction =42yds total, which equates 38.4m.
    The corresponding width for 1.0 fragment probability* of the 75mm Spgr.Patr.42 was 32.0m (= 35yds).

    Bottomline, using the same, albeit artificial method of comparison, the 75mm Spgr. fragment pattern is considerably deeper (129% advantage) than the M48´s in front of the burst but not quite as wide in the max side lobe (20% disadvantage).

    *) a metric difference in the measurement of penetrations are present in the US and german use of different systems. German data is referred to in probability of penetrations on a 1 square meter witness plate while US data in in relation to a one square yard size plate. Thus, considering that 1m = 1.0941 yd, it must be kept in mind that the data reproduced above are not corrected for this difference. Consequently, the german panel size is 19.7% larger than the US witness plate.

    1. You don't get to cast stones out "nonsensical ideas", given your bullshit in the T-28 article. If you were aware of the density differences between the crystal and cast/pressed forms of TNT you certainly made zero effort to mention that detail, so your post essentially read as "every modern density value for TNT is wrong because muh superior 70-year old German sauces"...

    2. The mistakes in the T28 thread are mistakes on Your account by incorrect interpretation of the german terminology, demonstrating a poor command of understanding the limitations implied by terminology and context.

      Plus, I never considered pure TNT in this thread and only referred to TNT as filler in projectiles (labelled Fp ´02), which has a lower density than Amatol used as filler. Which, of course, is the only practicable way of consideration when the context of comparison is to be a projectile explosion.

    3. Your fundamental mistake in that discussion started out at getting stuck at the terminology in the first place and failing to give any consideration to the practicalities of the matter.

      Your mistake HERE was to assume the Wikipedia figure is wrong *merely* because it doesn't match Forties German numbers - while quite failing to consider the possibility TNT could be (and is) pressed *denser*.

      For example, the '71 US handbook linked above records TNT density of 1.6 g/ml in the test shells used as benchmark (that's page 360 of the PDF incidentally). If the Germans didn't press theirs that much, well, their problem.

  6. Also of interest which I stumbled upon when Googling about Amatol:

    I only read the bit about the explosive specifically and eyeballed the historical overview at the beginning, but from the latter it is perhaps worth noting that the US Ordnance *specifically* regarded Amatol as a "substitute standard", ie. an inferior replacement, to TNT.

  7. That may be true for specific preconditions, as, f.e. Amatol has a less violent (=lower velocity) burst, lending credence to the idea of a finer degree of fragmentation and corresponding higher midbody = sideways directed projectile fragment velocity. This is also substantiated by several german fragmentation tests, including the one mentioned above. However, the smaller fragments lose velocity more rapidly than heavier pieces. Additionally, the blast effect to it´s adjacent area is measurably inferior to Amatol bursts but the ability of the higher velocity fragments to pierce steel is higher for TNT bursts, even while it drops off expectedly quicker than those of Amatol bursts. In total, the difference was not found to be supporting TNT when measured against effective penetrations at a certain distance to the burst -the principal reason why it was replaced as a filler by Amatol in german HE projectiles. While sideways fragment spray of TNT indeed reach a bit further out, the heavier nose pieces of Amatol burst reach out far further, too. The advantage of TNT was therefore only demonstrable by reducing the analysis on the sideways directed fragment pattern, and by ignoring other damaging effects, such as close blast and distant penetration effects.
    Therefore let´s speak the tests for themselves:

    M48 75mm HE shell (707g TNT filler) burst at 1080fps residual velocity front spray:

    .5 fragments: 22.3m
    1.0 fragments: 16.5m
    2.0 fragments: 11.9m

    normalized for 1 m^2 target panel and 1.0 perforations: 18.04m
    corresponding front spray reach for 75mm Spgr.Patr.42 (KWK, 680g Amatol): 38.0m at 1.0 perforations and 1m^2 target panel
    -huge advantage for the 75mm Spgr.Patr. 42 (>twice that of the M48)-

    side spray:
    .5 fragments: 42.0m (each side 21.0)
    1.0 fragments: 31.0m (each side 15.5)
    2.0 fragments: 22.0m (each side 11.0)

    normalized for 1 m^2 target panel and 1.0 perforations: 34.40m
    corresponding front spray reach for 75mm Spgr.Patr.42 (KWK, 680g Amatol): 32.0m at 1.0 perforations and 1m^2 target panel
    -small advantage (by 7.5%) for the M48-

    I maintain that in the end of the day, the larger TNT filler of the 75mm M48 shell does not translate into a larger fragment pattern over the smaller Amatol filler of the 75mm Spgr.Patr.42, considering everything, one might even argue for the opposite!

    1. Riddle me this: Amatol was *much* cheaper a shell filler than TNT. In terms of absolute explosive power at least some mixtures of it are also stronger.
      Why, then, did it not simply replace TNT in that use? Why, then, did Everyone & Dog, Inc. only resort to it as an economy measure - to get more working shells from a given tonnage of TNT? Why did militaries *prefer* to use TNT if they could?

      From what I've picked up on the topic the answer is quite succintly stated in the Sixties manual:
      "The brisance and power of an explosive determine applicability for specific purposes. A bursting charge must be brisant, but a ditching charge needs to be powerful and less brisant."

      TNT is quite a bit more brisant than Amatol so, yeah.

    2. Also not really sure what the point of that frontal fragmentation of the SprGr was in the first place. As far as I understand HE shells tend to be strongly optimised for lateral burst for good practical reasons; namely, you want to kill people *around* the point of detonation not *ahead* of it - most of the time fragments spat in the forward direction are just going to end up buried in mud or uselessly flattened against a wall or armoured plate anyway.

      And if you want directional antipersonnel air bursts (no idea if the tank shells even had fuzes for such; seems doubtful) just use a proper shrapnel shell already or something.

    3. TNT poured like Amatol could indeed reach a density of 1.6 from the tables of the Kiel institute but it was not poured into german shells but compressed into cubes, and -importantly- phlegmatised by beewax, resulting in a lower density of 1.58. Pure TNT is too sensitive for some applications.

      While TNT gives brisance (high velocity fragmentation and very small fragments causing very much damage closeby), Amatol gives better blast, more flash (setting alight things easier) and less brisance (fewer but larger fragments which go further but are less lethal closeby). Brisance by itselfe is often a tradeoff and to rate explosives just by one of the three damaging effects is not convincing.

      The considerably larger nose spray of the 75mm Spgr. was caused -in part- by shaping of the warhead and the size of the nose fuze segment in addition to what Amatol does in terms of fragmentation.

      Primary sources strongly imply that the germans were aware of the increased lethality in front of the shell.
      Gunners were instructed to deliberately aim slightly short of the target if the ground was normal, at the target if it was very soft (which would see a very large fraction of the nose pieces gone into the soil) and considerably short of the target if the ground was hard to allow for ricochet air bursts (with delay). So yes, we have to conclude that it indeed was practical for them.

      Shrapnel instead was already obsolete during ww1 and phased out of service shortly after.

      However, the point is that the 75mm HE was a potent high explosive round and it could be readily fired from the Panther´s 75mm L70 high velocity, frequently incorrectly charakterized "purpose designed anti-tank gun". The gun which are closest to the KWK 42 in terms of performance is the british 17pdr, with similar APCBC penetration but inferior HE.

    4. Again, that's a problem from the Germans. How you went from that to straight up claiming their number beat everyone else's I have no idea.

      And pure TNT self-evidently was not too sensitive to be used as a shell filler so not really seeing the relevance...

      Militaries quite universally opted for high-brisance shell fillers whenever they could. If you do not find the professional judgement of several generations of munitions engineers from multiple nations "convincing" then I honestly don't know what to say.

      Differences in the internal structure of the shell were my bet for the root cause of the frontal cone difference too - all other things being equal TNT should not magically have that different effects on the nose of the shell. I'm more curious whether that was merely a byproduct of the particular design used or a deliberately engineered feature (in which case one would have to question the priorities of the designers).

      And I think you're confusing "situational gimmickry" with "practical".

      "Purpose designed anti-tank gun" is only mutually exclusive with decent HE if you're a British engineer (judging by the evidence) so idk what the point of THAT digression was. Those guys are rightly notorious for having had their heads up their arses about it during the period.

  8. Summa summarum: the Soviet shell had straight up more metal to turn into fragments and in most models mentioned here ALSO a larger bursting charge of explosive better suited for the purpose.

    To claim it was for all practical intents and purposes the more potent HE shell thus appear to be quite legit.

    In practical terms I doubt the people on the wrong end would have noticed much meaningful difference between the two but that wasn't the topic anyway.


    1. The russian "explosive" area in their field handbooks for all projectiles as referenced in this article is NOT an actual explosive pattern -and I have seen enough of them to form an authoritative opinion-
      it´s a simplified box with no relevance to how a burst fragment pattern really looks like.

      I have instead given actual test result data for german and US 75mm HE, using similar methods to obtain the figure. Because the method is known and controlled and because the data are quantified rather than ill informed guesses, the extraction of conclusions out of the comparison is legitimate.

      If You have actual comparison data which are different, You are welcome to post them.

    2. You're welcome to explain how more steel being scattered around by a larger and more potent bursting charge does NOT add up to a more objectively powerful HE shell.

  9. You are generalizing blindly. Take a look into this sites description of 76.2mm projectiles, part 1 & 2. Fragmentation effect is not strictly correlated with highest amount of explosive, rather contrary, a more modest amount of Amatol is used to maximize fragmentation effect and a more extreme amount of TNT to maximize blast effect. This is quite comparable to the german approach with Amatol in Spgr. fragmentation projectiles.

    UO-353AM: 627g Amatol
    "The projectile is designed to produce the maximum number of lethal fragments. The KTM-1 fuze is used with the O-350 projectile in this round. The cast HE filler in the projectile is cavitated at the forward end to receive the booster."

    UF-352M: 820g TNT, "It gives greater blast effect and less fragmentation than the UOF-352 Frag-HE round."

    UOF-352: 710g Amatol 80. "The (...) projectile gives both fragmentation and blast effect; the setting of the fuze determines whether the fragmentation or the blast effect will be the greater, in any given instance."

    1. None of which particularly conflicts with what I said, or the overwhelming general preference for TNT as the burster whenever the economy allowed.

      And given what the German economic and resource situation was like already before the shooting started it's somewhat obvious the ability to fill something like twice the number of shells for a given tonnage of TNT was the overriding reason, considerations of ultimately rather minor performance differences be damned. Guns need enough shells to shoot *rather* more urgently than too few "perfect" ones.

  10. Well, if You don´t want to understand the explosive mechanic, and don´t accept primary sources demonstrating them, it´s pointless to have a discussion, right? So go on, comrade, go on live in Your phasntasie worlds...

    1. The general rule of thumb seems to be that the "slower" detonation of Amatol produces fewer, larger fragments that duly ceteris paribus fly longer for all the usual reasons. The "faster" detonation of TNT conversely produces more and smaller fragments.

      Insofar you're concerned with just the frag effects that's basically "area covered" versus "probability of hitting things within area"; the UO-353AM sounds like it was specifically designed as the artillery analog to "defensive" hand grenades.
      Also sounds like something that'd mostly get used by actual artillery batteries to cover large areas in frags which oughta be good for suppressing advancing infantry. The particular qualities don't seem overly relevant for tanks though?

      The other two models you helpfully listed have blatantly larger explosive fillers than the SprGr so thanks for proving my original point I guess? UF-352M sounds like it'd be the first pick for demolition work (potent and very large burster and doubtless by necessity thinner shell walls), UOF-352 more the general-purpose HE-frag munition (also cheap).

    2. This comment has been removed by the author.

  11. Now You are talking. But You still have to realize that the soviet data refute Your original presumption that a more violent, larger TNT burster produces automatically a larger fragment effect pattern than a smaller Amatol burster.

    The relationship between the damaging effects of blast-, fragmentation and heat (flash) is a fairly complex one and subtle changes represents tradeoffs in the various aspects, depending on what effect precisely -and at what distance- was preferred. The large number of different soviet period projectile designs indicates a larger number of concepts investigated in parallel and that standartization in this question was not yet obtained.

    I concur with the assessment on the type of choice to the different projectiles forwarded but want to remind that the article started with a conclusion in regard to "superiority" in 76.2mm HE effect, something which cannot be readily concluded from the different type of sources compared. HE patterns were a study on their own part and this article oversimplified this aspect.

    1. I never made any presumption of the kind you're referring to in the first paragraph.

      I merely stated the obvious about payloads.

      Given that the 76.2 mm was an *artillery* caliber first and foremost it's hardly surprising that a great variety of shell designs existed for different purposes - nevermind now that it had been in use almost two decades longer than the USSR had existed. Given that tanks have rather sharply limited stowage space for ammunition, and much of it in rather inconvenient places, I'd expect the preference was to load them up with the versatile all-purpose types rather than the various more specialised patterns.
      Plus the loaders had their hands full already with the basic shell classes without having to try to keep in mind and juggle different types of HE to boot. (There's recorded cases of loaders accidentally putting in something else than what the TC called for...) Given their working conditions KISS seems like an important rule of thumb to keep in mind.

  12. The strange thing with soviet projectiles -no pun intended- is that a great variety existed not only in HE but in AP designs, too, and that they did not stabilize their AP design until the early and mid 50´s, eventually adopting their german opponents design ideas.
    Many different projectile shapes cause a lot of logistic issues, for artillery, You´d need to issue new rangetables, f.e., unless the projectiles are matched ballistically, complicating firecontroll, too.

    I´d be happy to see the authentic 76.2mm HE fragment pattern diagramms based upon a controlled test. Once those are known, they can be compared with the pattern diagramms of other shells after some kind of normalization.

    I happen to know that the soviets made excellent mortar HE rounds from sources including their fragment pattern diagrams and would not be surprised to see them also making excellent HE projectiles. Yet these comparative data are not aviable yet.

    1. Technology Marches On, as it were, and different penetrator designs work differently against different types of armour plate. IIRC they changed their AP paradigm at least once to better match the face-hardening approach the Germans (for a variety of reasons) favoured, and postwar the concern was naturally... whatever design(s) it now was that the "Western" militaries used.
      And ofc the good old AP solid shot was by that point starting to get a little obsolete anyway, what with the rapid maturing of APCR/APDS/HEAT designs...

      No sure where projectile shapes enter the equation though. The laws of aerodynamics being pretty immutable you don't really want to mess with shell proportions, and as far as HE is concerned don't particularly need to anyway since you can just manipulate the internals.
      Want more blast effect? Thin out the shell walls to make more room for explosives (and spend less of the energy on bursting), use a more brisant filler, etc.
      Want bigger fragments? Thicken the walls, use a less brisant filler, etc.

      The diagrams in the linked article obviously isn't an in-depth technical test - the source in question being some kind of tactical handbook - but rather synthesised "ballpark estimates" of what the Soviet artillery considered the effective primary killzones of different calibers. Safe to assume they didn't pull those out of their asses.

  13. Sure. As they are primary sources, and intended to give the service personal reliable information on effect, I see no reason to question the factual content.
    However, the problem arise when secondary interpretations are extracted from two sources without any sensibility that they do not necessarely mean the same.

    F.e., did You notice that the soviet fragment rectangle in this service regulation pamphlet was based upon a "50% of the targets hit hit by fragment criterium"?
    Presuming that the target size was the same (this presumption has not been verified), this would equal the german 0.5 fragment hit criterium. However the latter was rarely ever quoted anywhere outside the prooving ground as the mode in german and US Army was to reference only the reliable 1.0 fragment hit criterium.

    Both, the US 75mm M48 and the german 75mm Spgr. have a sidespray reach considerably larger than the 76.2mm´s 30.0m at 0.5 fragment hits. The "superiority" of the 76,2mm depends on camparing apples with oranges...