76mm HE INFERIORITY

[rexford]

U.S. 76mm HE was grossly inferior to 75mm HE, and the following stats provide ample evidence of the differences:

75mm HE

3120 fps initial fragment speed

950 effective fragments at 20' from blast

105mm HE

3500 fps initial fragment speed

1010 effective fragments at 20' from blast

76mm HE

2260 fps initial fragment speed

560 effective fragments at 20' from blast

90mm HE

2900 fps initial fragment speed

672 effective fragments at 20' from blast

What the above data shows is that 75mm HE from the Sherman was almost as effective as 105mm howitzer HE, and quite superior to 76mm and 90mm HE. There are benefits to having a low muzzle velocity (we have heard that low velocity means less need for thick walls on HE shells, which allows more HE< but we are not sure on this).

The German 75mmL24 may have had similar benefits with regard to HE effectiveness when compared to 75L48 and 75L70. Short barrels shoot high potency HE.

Shermans with the 75mm gun were handy anti-personnel weapons regardless of what one might say about the APCBC.

[Guest Big Time Software]

<BLOCKQUOTE>quote:</font><HR>Shermans with the 75mm gun were handy anti-personnel weapons regardless of what one might say about the APCBC.<HR></BLOCKQUOTE>

I know that any German player that has had to withstand an unopposed assault by Sherman 75s can agree with you 100% I remember hearing German players wailing about this in two of the three initial Beta Demo scenarios.

Steve

[Guest jaja]

What is the difference in the HE shot between the 17 pounder and the 76.2mm guns?

[Vanir]

Hey, Steve. I'm bored so I thought I'd stir up some trouble

I have no idea what data you based the HE ratings on for CM, but if Rexford's data is correct, maybe they should be looked at again.

In CM the 75 is rated at a FP of 39 and the 76 at 33, which is 15.4 percent less than the 75.

Rexford's data says the 75 had 27.6 percent higher initial fragment speed and 41.1 percent more effective fragments (at 20' from blast).

Comparing the other two guns to the 75 we get:

75 vs. 105

Rexford:

105 10.9 percent greater fragment velocity.

105 6 percent greater number of fragments.

CM:

39 FP vs. 77 FP. 105 has 49.4 percent greater FP.

75 vs. 90

Rexford:

75 7.1 percent greater velocity.

75 29.3 percent more fragments.

CM:

39 vs. 56 FP. 90mm has 30.4 percent greater FP. Big difference!

I also have no idea if rexford is correct, or where he got his data, but he seems to generally know what he's talking about.

Food for thought I guess.

------------------

You've never heard music until you've heard the bleating of a gut-shot cesspooler. -Mark IV

[rexford]

Here is probability data for chance that effective HE fragments will hit 6 square foot target:

20' distance

100% for 75 and 105

80% for 90

67% for 76

35' distance

38% for 105

30% for 75

22% for 90

18% for 76

50' distance

19% for 105

13% for 75

10% for 90

8% for 76

100' distance

4.1% for 105

2.2% for 75

1.9% for 90

1.6% for 76mm

200' distance

0.8% for 105

0.4% for 75 and 90

0.3% for 76

Data comes from a TM that U.S. published during WW II, doesn't have title or number on the pages I have. Also shows blast shape and size, and armor penetration.

[rexford]

Long ago we read that 17 pounder HE was not especially potent due to high muzzle velocity, and Advanced Squad Leader was going to treat 17 pounder HE as something smaller.

The best HE comes from the low velocity guns. 75L24. 75L40.

German high velo guns fire HE at reduced speed.

We did a study and while high velocity is needed to hit vertical targets, low speed was better against a group of infantry in a field because flat trajectory fall on ground is highly influenced by vertical dispersion. Got to attack infantry crossing a field, bring on the close support 75L24.

75L24 could also fire cannister at human wave attacks due to absence of muzzle brake. And low velocity guns can indirect fire against relatively close targets, Panther can't. That is one reason why low speed howitzers are so valuable, big HE load and able to pop one in on a target with high arc fire.

[Jarmo]

Hey rexford! What are you?

By your use of the third person, I gather you are one of these:

(a) Royalty

( An entity of some kind

© A bunch of people

(d) Something else (this being correct in any case)

I'm genuinely interested BTW, not just being a wise ass.

I value your posts highly, learning something from each one.

[Guest Big Time Software]

Vanir - the blast ratings in CM are abstract amalgamations of the 'hard' data lying beneath and can't be used in linear comparisons to anything. They're just meant to provide a general sense of how powerful each weapon is.

One thing that I find puzzling about these numbers is that they don't show a greater difference between the 75mm and 105mm. After all not only was the 105mm projectile more than twice the size of the 75mm, but its muzzle velocity is lower which should only increase its relative effectiveness.

Charles

[dNorwood]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Jarmo:

Hey rexford! What are you?

By your use of the third person, I gather you are one of these:

(a) Royalty

( An entity of some kind

© A bunch of people

(d) Something else (this being correct in any case)

<HR></BLOCKQUOTE>

Or a scientist - we do this all the time (and yeah, it's just as pretentious as when royalty do it, but it's part of the union rules).

Ditto the GREAT value of rexfords posts - I'm finally starting to bridge the gap between my basic physics training and the applications to military technology. Lots of stuff here to "spice up" my lectures and make "F=ma" just a little bit more interesting.

[Guest Andrew Hedges]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Jarmo:

Hey rexford! What are you?

By your use of the third person, I gather you are one of these:

(a) Royalty

( An entity of some kind

© A bunch of people

(d) Something else (this being correct in any case)

I'm genuinely interested BTW, not just being a wise ass.

I value your posts highly, learning something from each one.<HR></BLOCKQUOTE>

I like the royalty idea. After all, "rex" means king.

[Keith]

The effectiveness of the 75mm Sherman is the reason why in late 44-45 the Sherman platoons always had a majority of 75mm equipped shermans even though the 76mm was in good supply. Something to keep in mind for historical scenario designers.

Regarding "spicing up" physics lectures just do some research on Descartes - the father of analytic geometry and the theory of momentum. The guy was a part time swash buckling mercenary and general. I recall reading he once got jumped on a boat by a bunch of bandits and proceeded to cut them to pieces in a sword fight.

[Guest Michael emrys]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Keith:

Regarding "spicing up" physics lectures just do some research on Descartes - the father of analytic geometry and the theory of momentum. The guy was a part time swash buckling mercenary and general. I recall reading he once got jumped on a boat by a bunch of bandits and proceeded to cut them to pieces in a sword fight.<HR></BLOCKQUOTE>

"I fence, therefore I am."?

Michael

[rexford]

Rexford means King's Crossing, or King's Fiord.

Grandfather was half Mohawk "indian" (native american} named Dexter who won a load of medals during WW I, and fought in all the major battles that America was part of (including Meuse-Argonne, I believe). Even won the Croix de Guerre, the French were happy when other people fought the Germans.

Following presents muzzle velocities for British HE and smoke, which is an interesting addition to earlier discussions:

3" tank howitzer 600 fps HE!!!!

95mm tank howitzer 1050 fps HE & 746 fps smoke!!!!!

6 Pdr tank gun 2675 fps HE

75mm M3 1550 fps HE & 850 fps smoke

2100 fps super charge (good for shooting through bunker openings when pinpoint accuracy is needed).

Hitting a vertical target with a 3" tank howitzer would be an adventure beyond close range, but tanks with this gun were called "close support".

Low velocity of smoke suggests thin walls to allow max chemicals, so not too much stress.

(aside: Firefly had 3x/6x interchangeale gun sight, makes sense to easily see and target long range targets)

Why is 75mm HE so potent when 105mm HE is also low velocity? Don't know. The data presented in previous messages is official American data which appears to be from field tests, and we never pursued the why's any further.

We would be interested in an explanation if anyone has or finds one.

We had, and still may have German data on HE charge size within all of the tank gun shells. Here are German HE muzzle velocities:

50L60 550 m/s (1804 fps)

Data goes out to 6500m!!!!(?) Long range HE bombardment by Puma's?

75L48 550 m/s (1804 fps)

75L70 700 m/s (2296 fps)

76.2L51.5 550 m/s (1804 fps)

88L56 810 m/s (2657 fps)

88L71 750 m/s (2460 fps)

"88" HE muzzle velocities seem kind of high, must have been for hitting anti-tank guns on the fly.

Low velocity for smoke is interesting, no pinpoint accuracy with that muzzle velocity.

German ballistic data for HE shells gives longitudinal distance for 50% of shots. For 810 m/s 88L56 HE, "lange" for ground dispersion on level ground is 107m at 2000m, so if range estimation is perfect than 50% of shots fall within a 351' long distance centered on 2000m range and running along the firing line.

Longitudinal scatter for 75L48 HE at 550 m/s is 54m at 2000m, or 50% of HE shots fall within a 177' long distance centered on 2000m and running along the firing line.

The longitudinal fall of shot is due to fact that flat trajectories are heavily influenced by vertical scatter, while lower velocities are not as impacted.

3" British howitzer at 600 fps or 75L24 HE would have a very small longitudinal dispersion about 2000m range if it followed the abovenoted German trend.

How far afield do German HE rounds fall from the intended point: 50% of 75L48 HE shots at 2000m will fall within 1.6m of firing line after jump and other factors are cranked in.

HE shots should not fall 100m left or right of target, under normal circumstances.

For those who are interested in ballistics, William Jurens wrote a paper entitled EXTERIOR BALLISTICS WITH BALLISTICS that is the single best work on the subject, in our opinion. Has drag coefficients, equations and a computer program in BASIC that computes elevation, angle, etc. for shots and prints out results every 50m or so. The paper ran in a naval magazine, and an internet search on Mr. Jurens' name might identify a current source (we haven't had time to do this).

The paper covers naval rounds and it is easy to apply findings to WW II anti-tank stuff.

[Guest Germanboy]

<BLOCKQUOTE>quote:</font><HR>Originally posted by rexford:

50L60 550 m/s (1804 fps)

Data goes out to 6500m!!!!(?) Long range HE bombardment by Puma's? <HR></BLOCKQUOTE>

Was that the same 50mm gun as in the later Panzer III? In that case Afrika Korps may have had engagements approaching that range. Just a guess.

------------------

Andreas

Der Kessel

Home of „Die Sturmgruppe“; Scenario Design Group for Combat Mission.

[Tiger]

<BLOCKQUOTE>quote:</font><HR>We did a study and while high velocity is needed to hit vertical targets, low speed was better against a group of infantry in a field....<HR></BLOCKQUOTE>

Just curious, this wasn't one of those college courses "volunteer for extra credits as a infantryman to help us in our study" was it? Hmmm?

john

[Vanir]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Germanboy:

Was that the same 50mm gun as in the later Panzer III? <HR></BLOCKQUOTE>

Correct. Pz III Ausf J and later.

------------------

You've never heard music until you've heard the bleating of a gut-shot cesspooler. -Mark IV

[Vanir]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Big Time Software:

Vanir - the blast ratings in CM are abstract amalgamations of the 'hard' data lying beneath and can't be used in linear comparisons to anything. They're just meant to provide a general sense of how powerful each weapon is.<HR></BLOCKQUOTE>

I guess this goes against one of the assumptions I had about CM. I thought the HE numbers were FP ratings same as any other unit has. For example, the M1919 MMG has a FP rating of 40 at 250 meters, so it would do about the same damage with a hit at that range as a 75mm shell from a Sherman (HE rating of 39).

So I guess you're saying these numbers represent different things and are not comparable?

------------------

You've never heard music until you've heard the bleating of a gut-shot cesspooler. -Mark IV

[KiwiJoe]

If sherman 75mm HE rounds were as bad ass as rexs says I'd be buying M4A3's and the like quite often. Pretty cheap, high rof, ammo load and turret speed mixed with wicked blast would be 1 mean infantry killer. At the moment I find the 75mm only "slightly" better vs infantry the 76mm ( as the 33 vs 39 blast rating would suggest). If you couple that with its lack of AT abilitly they currently just arent worth buying.

[Guest Michael emrys]

<BLOCKQUOTE>quote:</font><HR>Originally posted by KiwiJoe:

If sherman 75mm HE rounds were as bad ass as rexs says I'd be buying M4A3's and the like quite often. Pretty cheap, high rof, ammo load and turret speed mixed with wicked blast would be 1 mean infantry killer.<HR></BLOCKQUOTE>

That's what I do. If I think there is a chance of running into any German armor, I will also buy a couple of 76mm armed tanks or TDs as well.

Michael

[Guest Big Time Software]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Vanir:

ISo I guess you're saying these numbers represent different things and are not comparable?

<HR></BLOCKQUOTE>

Right. The actual blast power applied to a target depends on how close the target it to where the shell explodes. A few meters can make a big difference. That said, the blast numbers are roughly in line with the firepower numbers in terms of relative sizing, but direct comparisons aren't 100% accurate.

Charles

[Simon Fox]

The relative effectiveness of HE rounds is not always intuitively obvious as indicated by some of the comments here. Many factors other than merely velocity and projectile size (charge) seem to be involved and generally comparisons often seem to be qualitative in nature.

For example the British 25 pdr was considered to have really good killing power for it's size. They considered it superior to the US 105mm even though it was larger and hence it was one reason for the switch to Sextons ASAP. Aussie units who used Italian 75mm and 100mm howitzers as well as 25 pdrs found the latter were much more effective (by a very wide margin).

I have read that the 17pdr HE was not as good as the 75mm and my impression was that the difference was noticeable which isn't really so in CM. Even so I have also read the 17pdr HE was very good for "bunker-busting" and used for that purpose frequently.

These anecdotal but widely remarked differences aren't necessarily found in CM because BTS probably just used the basic features of the shell/gun to determine such things. There are some good Brit studies too on artillery lethality (for Tigers benefit they used sheep and dummies) and fragment dispersal patterns and density etc. These could be useful. For example IIRC they found the German 81mm mortar had better accuracy and range than the 3in but the latter had greater 'lethality'.

------------------

Muddying the waters as usual.

[Conall]

<BLOCKQUOTE>quote:</font><HR>Originally posted by rexford:

(aside: Firefly had 3x/6x interchangeale gun sight, makes sense to easily see and target long range targets)

<HR></BLOCKQUOTE>

Just to clarify this the Firefly was equipped with the No. 43 Mk3/1 telescope which had a x3 eyepiece or a x6 eyepiece. These were not interchangeable in combat - nor could the higher magnification be selected in the same way as the dual magnification German telescopes (Tzf9d etc). A Guide to A.F.V. Telescopes

Author: A.F.V. Publications Section, A.F.V. School, Bovington Camp

Date of publication: March 1945

Publisher: War Office, A.F.V. Publications Section

Page number(s): 6

On the subject of the Firefly's HE shell here is a little more information:

The 17pdr fired two types of HE shells- the HE Mk 1 T shell (HE-T), weight 34.2 pounds (complete round), 15.4 pounds (projectile). During 1944 a reduced charge round (1,800 fps MV instead of 2,950 fps) was produced which allowed thinner walls for the shell & therefore a higher HE filler. See War Office Document 291/1268 for details of ranging, dispersion & bracketing procedure for 17pdr gun with HE ammo mks IT & IIT reduced charge, date 1944. Also see Hunnicut's "Sherman" p.565

<BLOCKQUOTE>quote:</font><HR>

For those who are interested in ballistics, William Jurens wrote a paper entitled EXTERIOR BALLISTICS WITH BALLISTICS that is the single best work on the subject, in our opinion. Has drag coefficients, equations and a computer program in BASIC that computes elevation, angle, etc. for shots and prints out results every 50m or so. The paper ran in a naval magazine, and an internet search on Mr. Jurens' name might identify a current source (we haven't had time to do this).

The paper covers naval rounds and it is easy to apply findings to WW II anti-tank stuff. <HR></BLOCKQUOTE>

You need to order a backcopy of Warship International produced by the International Naval Research Organization www.primenet.com/~inro I have a feeling that the article on Exterior Ballistics with Microcomputers is in Issue No 1 1984 & is still available.

Hope that helps

Best regards,

Conall

[rexford]

For first shot HE at infantry in low brush woods, 75 HE will cause 30% more casualties than 76mm, based on our calculations.

The 75mm advantage is based on these factors:

1. More fragments and higher velocity pieces

2. Lower HE velocity than 76mm, which means less ground scatter

German data shows that flatter trajectories have longer ground scatter along the firing line, since random up-and-down dispersal effects flat trajectories more.

On follow-up shots, the 75mm HE advantage should increase.

Thanks Conall for tracking down the Jurens article. The article listed the BASIC program steps but Mr. Jurens provided a 5 1/4" floppy with the program, which I still have.

[aka_tom_w]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Conall:

Just to clarify this the Firefly was equipped with the No. 43 Mk3/1 telescope which had a x3 eyepiece or a x6 eyepiece. These were not interchangeable in combat - nor could the higher magnification be selected in the same way as the dual magnification German telescopes (Tzf9d etc).

A Guide to A.F.V. Telescopes

Author: A.F.V. Publications Section,

A.F.V. School, Bovington Camp

Date of publication: March 1945

Publisher: War Office, A.F.V. Publications Section Page number(s): 6

Conall<HR></BLOCKQUOTE>

GREAT reference!!

Is there any chance Charles and Steve can get a copy of this as it may come in handy when attempting to determine some long range optics advantage to for gunnery accuracy to be modeled in the up coming CM2??

That sounds like a VERY detailed and informative articel there! How can Steve and Charles get a copy of it? Or do they have it already?

Keep up the GREAT postings Rexford they are fascinating to read!

-tom w

[Conall]

<BLOCKQUOTE>quote:</font><HR>Originally posted by aka_tom_w:

GREAT reference!!

Is there any chance Charles and Steve can get a copy of this as it may come in handy when attempting to determine some long range optics advantage to for gunnery accuracy to be modeled in the up coming CM2??

That sounds like a VERY detailed and informative articel there! How can Steve and Charles get a copy of it? Or do they have it already?

<HR></BLOCKQUOTE>

If they ask me nicely & feel they need them, then I'll happily scan them my copy.

regards,

Conall

[This message has been edited by Conall (edited 01-07-2001).]