Long Range Tank Gunnery -- Again

[jwduquette1]

One note - don't know if actualy usefull but here it is:

In Yugoslav service modernised 88mm M18/36/37 coastal guns (Yes, that is WW2 German 88mm flak) in the mid-80s (included SNAR-10 radar and LRF with balistic computer) would regulary acheave 1st round hit with salvo fire (eg 6 guns from same battery would fire) at 7-8km. Target was 2 x 10m panel towed behind a boat at 15-20km/h.

Note that in salvo fire "first round hit" is considered on the battery level - so if only one gun out of six hit it would still be considered "first round hit".

 

For the individual guns firing to "pass" your crew had to do at least 50% with 10 rounds. Most crews did about 6-7 with some getting to 9-10.

 

Unfortunetly I don;t have a data for the gns w/o balistic computers/LRFs/radars to compare.

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Hi Bojan:

 

Interesting stuff. I have dispersion data laying around here for the German 88mm. But this would have been circa-WWII pzgr or spgr. There would have had to have been a considerable improvement in ammunition accuracy for the Yugoslavian coastal 88s to be consistently hitting with this sort of rate at ranges of 7 to 8Km. I have attached the 50% dispersion zones (in mils) for 88mm pzgr. The width of the dispersion zone (in mils) remains relatively constant with range. However the spread in height is not uniform in mils – it is steadily increasing with range. Just to be clear I am not doubting what you are saying. I am just interested in back calculating what sort of ammunition dispersion pattern would be required to achieve the level of accuracy you are talking about.

 

The towed target that you described – is it 2-meters in height – or is it 10-meters in height?

 

Regards

Jeff

 

[jwduquette1]

Love to go OT on naval and CD gunnery, my early interests, Jeff. The fighting tops [tripod, cage mast mounted] contained spotting stations, but the director was too large and cumbersome [later became almost a turret in its own right] to be up there, usually placed uppermost on the forward superstructure [crowning the conning tower armored structure in modern ships], and later a secondary one [still for main armament] placed in the after structure. Secondary & AA batteries could have their own directors, placed at less advantageous heights and positions as designs permitted.

 

Naval gunnery, even direct fire [battery local control], remained shot, spot, shot, spot in order to gain straddles. I had my tankers man a twin 3"/50 mount to fire local surface competition with the other 5 mounts of USS Hermitage (LSD), using a goldplated gun crew with 2 of my TCs as gunner, a-gunner, my GySgt as mount captain. We used BOT [with their iron-ring AA sights] and knocked the navy dicks in the dirt, so to speak, at 2-3000 yds.  Ken

 

[edit to add: NJ [and others?] did sink an IJN DD at very long range with radar as they finally arrived at San Bernadino Strait in TF34, too late for the Sama Battle at Leyte Gulf '44. I think they sank Nowake?]

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Hi Ken:

 

Great stuff. The radar shoot I was referring to was Iowa and New Jersey firing at the Nowaki. This was somewhere in the vicinity of Truk. The two BB's cease fire at 39000-yrds. Nowaki got away undamaged.

 

This is totally off topic, but you had been talking about accuracy of early 90mm HEAT rounds. This was a few months back on a thread that I can't recall the title of. Anyway I came acrosst’ a report from BRL detailing the accuracy issues with 90mm T108 HEAT. The shot dispersion -- as you had implied before -- was pretty large. Even at ranges of only 500 to 1000yrds. The report ID'd two issues.

 

The first problem was determined to be jump resultant from high yawing velocity. This was attributed to be fin damage\deformation occurring as the projectile moved down the tube of the 90mm gun. They were able to trace it directly to fin material strength – the higher strength fins were deforming far less than the lower strength fins (go figure).

 

The second problem was traced to resonance. At certain roll rates the steady state yaw was found to increase dramatically. If they had designed the round to spin a little faster or a little slower it would have been fine – very low steady state yaw. However the actual design, compounded by the fin deformation described above, was resulting in very high levels of yaw. As the yaw angle gets bigger, the drag increases, and accuracy decreases. Shot-to-shot variations became relatively large and the trajectories become unpredictable.

 

The 50% Zone @ 1000-yrds for this projectile was reported to be a whooping 1.28-mils(!) and 1.74-mils(!) in the horizontal and vertical planes respectively.

 

Sorry – that was totally off topic, but I couldn’t remember the other thread we had been talking about this issue so I posted it here.

 

Regards

JD

[Guest bojan]

Hi Bojan:

Interesting stuff.  I have dispersion data laying around here for the German 88mm.  But this would have been circa-WWII pzgr or spgr.

 

Ammo used was overhauled german stuff - german cases and shells, local gunpowder, US fuses.

 

There would have had to have been a considerable improvement in ammunition accuracy for the Yugoslavian coastal 88s to be consistently hitting with this sort of rate at ranges of 7 to 8Km.  I have attached the 50% dispersion zones (in mils) for 88mm pzgr.  The width of the dispersion zone (in mils) remains relatively constant with range. However the spread in height is not uniform in mils – it is steadily increasing with range.  Just to be clear I am not doubting what you are saying.  I am just interested in back calculating what sort of ammunition dispersion pattern would be required to achieve the level of accuracy you are talking about. 

From what I have gethered once you got over certain range (3-4k meters) dispersion of the 88 would not increase much more. That might be an answer.

 

The towed target that you described – is it 2-meters in height – or is it 10-meters in height?    

 

My guess is 2m height, 10m lengts (representing small lending/patrol craft).

 

Edit - Damn it is 20x10m... That would explain it...

Edited July 1, 2006 by bojan

[DKTanker]

From what I have gethered once you got over certain range (3-4k meters) dispersion of the 88 would not increase much more. That might be an answer.

My guess is 2m height, 10m lengts (representing small lending/patrol craft).

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The angular dispersion might not increase but I can't believe the actual dispersion doesn't increase.

[Ken Estes]

I have this surrealistic impression of the northern Med/Adriatic ringed with ex-Wehrmacht 88s. Spain kept theirs in AA and into the late 80s as CD weapons. I wonder if the CD weapons emplaced in France, Italy Greece were kept in commission very long. I suppose Turkey had some export 88s....

[Guest bojan]

The angular dispersion might not increase but I can't believe the actual dispersion doesn't increase.

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It does, but it apears that it is small enough that 20 x 10m can be hit reliably at long range.

[Guest bojan]

I have this surrealistic impression of the northern Med/Adriatic ringed with ex-Wehrmacht 88s.

 

88s were actualy high end of guns used - here is what Yugoslavia used:

 

3"mm Mk.3 (UK) and M3 (US) AA guns (reserve, semi mobile positions);

3/50, 5/38 (US) and 4.something" (UK) guns from the decomisioned frigates/destroyers (fixed positions on the islands from the mid-late '60s);

76mm model 31 and model 38 AA guns (Soviet) (on the Skadar Lake toward Albania, retired in late 70s, replaced with 85mm)

Italian 75mm and 90mm AA guns (75mm were reworked to acept US 76mm and 90mm to US 90mm ammo) - part of coast near Italy.

Soviet 85mm model 39 and 44 AA guns - Dalmatian coast. One of those damager Koni class frigate "Split" in 1991, near Split (talk about irony).

88mm AA guns - Montenegro and Dalmatian coast, some upgraded in '80s, served until late 2004! Picture of the modernised one in 2002.

US 90mm and UK 94mm - Istra.

130mm M46 - mobile.

Lot of older guns were also in reserve - those things were sometimes as ancient as Skoda 66mm that was kept until mid '60s...

 

There were two projects to replace all those fixed guns with 100mm - one ws based based on the T-12 ATG with a smoothbore barrel (PIC) and while other used longer D-10 based barrel ( but longer - L/68 vs L/56) and ammo compatible with T-55. First one had 12 produced in Novi Travnik and some saw use in Bosnia in standard AT/fire support role. 2nd prototype had also 12 proiduced and those were used by Croatia until 2003-4.

Pictures of firing:

1

2

3

4

 

Spain kept theirs in AA and into the late 80s as CD weapons. I wonder if the CD weapons emplaced in France, Italy Greece were kept in commission very long. I suppose Turkey had some export 88s....

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Italy kept their CD until early '90s.

Greece had tuntil at least early '80s.

Edited July 2, 2006 by bojan

[M1Buck]

Dave:

 

I figure you are probably tired of answering these sorts of questions – but if you’ll indulge me once more about your description of sight zeroing right before the start of Desert Storm.  You indicated your battalion had been allotted three or four rounds per tank of M829 to zero.  Did you zero both your GPS and GAS using this same shot pattern?

 

Thanks again.

Regards

JD

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The proceedure is to align the GAS w/ the GPS after GPS has confirmed it's zero.

[DKTanker]

The proceedure is to align the GAS w/ the GPS after GPS has confirmed it's zero.

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I never did, for the reasons I gave. Never had any problems with the BS enagagement either.

[M1Buck]

I never did, for the reasons I gave.  Never had any problems with the BS enagagement either.

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You probably won't with the close range of that engagement. The only time is when you "need" it is when your GPS fails. If that happens on a gun range, you back off and get your tank fixed. If in combat, you got problems.

[DKTanker]

You probably won't with the close range of that engagement.  The only time is when you "need" it is when your GPS fails.  If that happens on a gun range, you back off and get your tank fixed.  If in combat, you got problems.

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OTOH, not using boresight knob correction factors but rather simply refereing your GAS to your GPS does nothing for you when it's HEAT you want to shoot. Hard to align your sights when that GPS has failed in combat.

[jwduquette1]

Ammo used was overhauled german stuff - german cases and shells, local gunpowder, US fuses.

From what I have gethered once you got over certain range (3-4k meters) dispersion of the 88 would not increase much more. That might be an answer.

 

Edit - Damn it is 20x10m... That would explain it...

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Hi Bojan:

 

I assume the target sleds were 10m in height and 20m in length? Moreover 20m of freeboard is somewhat unusual for a warship. The USN used to use target rafts -- "battle rafts" -- that were about 20 to 40-ft in height, and about 3 to 4 times that dimension in length. 20-ft by 140-ft towed battle rafts were used to represent destroyer sized targets, and 40-ft x 140-ft towed battle rafts were used to represent anything from a cruiser to a battleship. They also employed smaller "target sleds" in a variety of sizes and shapes.

 

Regards

Jeff

[Guest bojan]

Hi Bojan:

 

I assume the target sleds were 10m in height and 20m in length?  Moreover 20m of  freeboard is somewhat unusual for a warship.  The USN used to use target rafts -- "battle rafts" -- that were about 20 to 40-ft in height, and about 3 to 4 times that dimension in length.  20-ft by 140-ft towed battle rafts were used to represent destroyer sized targets, and 40-ft x 140-ft towed battle rafts were used to represent anything from a cruiser to a battleship.  They also employed smaller "target sleds" in a variety of sizes and shapes.

 

Regards

Jeff

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10m high, 20m long. It was basicly thin Al sheet that was set on the frame. Those were probably ment to represent landing ships - after all primary CD role of the guns was anti-landing.

 

Worst thing that could happen is that someone on the first shot hit the frame and whole thing went into the water...

[jwduquette1]

Thanks Bojan.

 

Attached are the 50% Zones for 88mm Flak 36 firing spgr (high explosive shell). Again, this represents circa-WWII data from German schusstafeln. The tables don’t go out to 7Km for pzgr. However the HE\spgr round is actually slightly more accurate than the AP\pzgr projectile.

 

HE Shot to Shot Spread 88mm Spgr

 

 

Inherent\systematic deflection errors in shot spread don’t typically control for targets sleds of this size -- this all assumes no human error like miscalc'ing lead or the like. Inherent range errors are much greater and will therefore end up controlling final hit probability when considering shot-to-shot dispersion by itself.

 

In naval shoots (this is USN gunnery terminology circa WWII lest we confuse one of our readers again) descent angles in excess of about 3 or 4-degrees entail determination of probable hit rate from the length and width of the dispersion zone rather than height and width. In the case of the 88mm firing spgr this would be any shoots beyond about 4km to 4.5km in range.

 

The target sled dimensions are converted into what the USN would call the “hitting space”. The hitting space is a simple function of real target sled\raft length by the target freeboard times the cotangent of the descent angle. In other words the horizontal target footprint becomes much larger than the nominal size of the target sled due to the projectiles descent angle. Typically some additional area is added to the area immediately in front of the target to account for near misses that still succeed in striking the hull below the waterline. I don’t think this was usually done for gunnery training against sleds\rafts as these are shallow draft contraptions, but I threw in some additional slop just to give the shooters a bit more hit probability advantage. For heavy caliber shells like 14 to 16-inch shells this space can be up to 15-yards in front of the target ships hull. Mid-caliber like 8-inch is more like 3 or 4-yards. I assumed for 88mm this near miss space would not be much more than a meter in front of the target raft.

 

The hitting space parallel to the line of fire becomes:

Freeboard x cotangent(decent angle) + 1m.

 

In deflection the hitting space is simply the length of the target.

 

For a 7000m shoot using 88mm spgr. the hitting space for a 10m x 20m target sled works out to be:

Descent Angle for 88mm spgr at 7Km = 12.75-degrees

Freeboard of target sled = 10m

Hitting Space in range = [10m x COT(12.75-deg)] + 1m = 45.2m

Hitting space in deflection = 20m

 

As you can see the hitting space in range is much smaller than the length of the 50% Zone of the projectile at 7km. We can therefore deduce that the hit probability for shot-to-shot dispersion alone will have to be less than 50%. Actual length of the 50% Zone is about 73m at 7Km. 73m > 45.2m

 

In deflection there is no problem. The 99.999% Zone for shot dispersion in deflection -- even at 7Km -- is totally encompassed by the width of the target sled. This assumes a center of target aim point and no laying errors or lead errors.

 

The hit probability from inherent shot spread will therefore be a function of only inherent\systematic range error. In this case, the hit probability at 7km from shot spread alone works out to be approximately 35.5%. This assumes a center of visible mass aim point and no errors in the range estimate or gun lay, and the gun and sight combo are properly calibrated, etc, etc, etc. To get to at least a 50% probability of a hit from shot spread alone, the length of the 50% Zone has to be reduced to the size of hitting space presented by the target raft (or less). The 50% Zone in range would have to be equal to, or less than about 45m. The actual 50% Zone is about 73m in range at 7Km. In other words ammunition improvements would have had to have resulted in about 40% reduction in inherent\systematic range errors from the circa WWII spgr. ammunition.

 

Regards

Jeff

Edited July 4, 2006 by jwduquette1

[M1Buck]

OTOH, not using boresight knob correction factors but rather simply refereing your GAS to your GPS does nothing for you when it's HEAT you want to shoot.  Hard to align your sights when that GPS has failed in combat.

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That is why you record your numbers off the GAS boresight nobbs then do the same for HEAT and "develop" the GAS sight corrections for that ammo. The only time this whole excercise is relavant is combat w/ GPS failure IMHO.

[nigelfe]

Thanks Bojan.

 

Attached are the 50% Zones for 88mm Flak 36 firing spgr (high explosive shell).  Again, this represents circa-WWII data from German schusstafeln.  The tables don’t go out to 7Km for pzgr.  However the HE\spgr round is actually slightly more accurate than the AP\pzgr projectile.

 

HE Shot to Shot Spread 88mm Spgr

 

 

Weird, or at least highly unusual, the graph states that at 500 m range PEr is 35 m and at 10,000 m it's about 37 m. Assuming this represents surface to surface fire, its the same cartridge at all ranges and that horizontal max range is about 15,000 m. At best I'd have expected PEr to be a fairly consistent % of range, perhaps a bit up at short range and increasing as max range is approached. It's stretching my credulity.

[DKTanker]

That is why you record your numbers off the GAS boresight nobbs then do the same for HEAT and "develop" the GAS sight corrections for that ammo.  The only time this whole excercise is relavant is combat w/ GPS failure IMHO.

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Think about it.

[M1Buck]

Yeah, I know. I guess the thought process is to develop the tanker to the FCS logic and to get good habits ingrained.

[jwduquette1]

Weird, or at least highly unusual, the graph states that at 500 m range PEr is 35 m and at 10,000 m it's about 37 m.  Assuming this represents surface to surface fire, its the same cartridge at all ranges and that horizontal max range is about 15,000 m.  At best I'd have expected PEr to be a fairly consistent % of range, perhaps a bit up at short range and increasing as max range is approached.  It's stretching my credulity.

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I cant help your credulity . The numbers are the numbers. Get yourself a copy of the firing tables -- after which maybe we will have something to disscuss.

Edited July 5, 2006 by jwduquette1

[DB]

I cant help your credulity  .  The numbers are the numbers.  Get yourself a copy of the firing tables -- after which maybe we will have something to disscuss.

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If I read the graph correctly, the length parameter uses the right hand scale, and so the length of the footprint varies from 69 to 75 metres over the range, suggesting that the increase in dispersion with range is compensated for by some other effect - a combination of increasing angle of impact and decreasing horizontal velocity, I would suspect. Really rather interesting and non-intuitive, but perhaps indicative of direct fire in comparison to indirect?

 

David

[jwduquette1]

If I read the graph correctly, the length parameter uses the right hand scale, and so the length of the footprint varies from 69 to 75 metres over the range, suggesting that the increase in dispersion with range is compensated for by some other effect - a combination of increasing angle of impact and decreasing horizontal velocity, I would suspect. Really rather interesting and non-intuitive, but perhaps indicative of direct fire in comparison to indirect? 

 

David

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You are reading the figure correctly. Increasing angle of impact and velocity drop are doubtless part of what we are seeing.

 

Below are the lengths of the 50% Zones vs. Range as indicated in the 1939 Range Tables for the 25-pdr’s H.E. streamline projectile. Obviously the creators of this set of tables have done a bit of rounding. Moreover we shouldn’t really believe the 50% Zone is a uniform 20-yards in length starting from 3000yrds and extending out to a range of 7000yrds. Suddenly at the magic distance of 7100yards the length jumps to 40-yrds. I suppose if one were irritating enough one could make some hay here. But than that would be pretty silly.

 

In essence the rate of change for the size of the 50% Zone is very small up to about 6500 to 7500-yards. (Actually the rate of change is zero if we were to take the range table data literally). But again, that would be silly – right? At a range of about 6500 to 7500-yards we start seeing a much greater rate of change in the length of the 50% Zone vs. range. Lest the question arise, the 25-pdr RTs don’t indicate anything for the 50% zone at ranges less than 3000-yrds. More hay. The point being that the low rates of change in the length of the 88mm spgr. 50% Zone don’t appear to be particularly weird, or highly unusual when compared to the 25pdr streamline data.

 

But in the interest of furthering my own education, I guess my question would be why does the 88mm spgr. range errors appear weird, or highly unusual? What’s the basis of this suspicion?

 

[jwduquette1]

Below is a comparison of the length of the 50% Zones vs. Range for 25-pdr Streamline HE and 88mm Flak 36 firing spgr. The shapes of the curves are similar in that there is a relatively flat portion of the curve with low rates of change in the length of the 50% Zone. This low rate of change gives way to a fairly steep portions of the curves and high rates of change in the length of the 50% Zone as the projectile approaches its maximum range.

 

[nigelfe]

If I read the graph correctly, the length parameter uses the right hand scale, and so the length of the footprint varies from 69 to 75 metres over the range, suggesting that the increase in dispersion with range is compensated for by some other effect - a combination of increasing angle of impact and decreasing horizontal velocity, I would suspect. Really rather interesting and non-intuitive, but perhaps indicative of direct fire in comparison to indirect? 

 

David

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Every RT/FT I've ever looked at (and that's a heck of a lot from pre-WW1 to modern) the PE at a range is also at the elevation for that range, therefore they reflect actual velocities and angle of descent. Of course one possibility is that they are not standard surface to surface fire figures, but some strange (to me) AA thing.

 

The normal surface to surface pattern is that PEr increases noticeably with range Fig 4 on the Errors & Mistakes page of my web site at http://members.tripod.com/~nigelef/index.htm you'll find a graph for mostly WW2 guns plotting % PEr against range. They do show a peak at short range but in part this reflects UK RTs rounding 50% to the nearest 10 yards. Note that the most modern gun, with FTs that give PEr to the nearest m has a fairly flat curve.

 

The PErs (ie half 50%) for 88mm go from some 35 m to 38 m over 9500 m, this would give a downward curve. The obvious check comparison is 3.7 in HAA or 90 mm AA RT/FT, it'll be a couple of months before I can get my hands on the former (for surface to surface fire) and I haven't a clue where to find the latter.

 

Incidentally the 25 pr RT data quoted is not entirely correct, it looks as if its Chg 3, whereas Chg Super would be a better match to 88mm, I have 25 pr 50%s down to 1000 m. A complete list of 25 pr RTs can be found on the 25 pr page of my web site, there's quite a lot of them! I've also got a recollection that the chg 3 50% were subsequently updated in one of the editions after 1939 (something I stumbled on when doing the graph for my web site). Just for the record and to correct mistakes, the 25 pr Chg Super 50% at each 1000m from 1000m to 12000m are (including the 88mm extreme points in brackets): 30 [69], 30, 40, 50, 50, 60, 60, 70, 70, 80 [75], 90, 90. The progression is obvious. I hope this makes my point about 88mm being weird a bit clearer.

 

However, after some digging I've found one instance that's a similar pattern - 175mm Chg 1 Green, max rg 15km, 50% @ 1000m 46m, @ 10,000m 46m, and it actually dips in between! However this is a far heavier shell and far lower MV than 88mm, and Chg 1 White goes from 92m to 230m for the same ranges! I've also come across people who have regarded the PE data for 175mm with some suspicion (putting it mildly).

Edited July 6, 2006 by nigelfe

[jwduquette1]

Every RT/FT I've ever looked at (and that's a heck of a lot from pre-WW1 to modern) the PE at a range is also at the elevation for that range, therefore they reflect actual velocities and angle of descent.   Of course one possibility is that they are not standard surface to surface fire figures, but some strange (to me) AA thing.

 

The normal surface to surface pattern is that PEr increases noticeably with range Fig 4 on the Errors & Mistakes page of my web site at http://members.tripod.com/~nigelef/index.htm you'll find  a graph for mostly WW2 guns plotting % PEr against range.  They do show a peak at short range but in part this reflects UK RTs rounding 50% to the nearest 10 yards.  Note that the most modern gun, with FTs that give PEr to the nearest m has a fairly flat curve.

 

The PErs (ie half 50%) for 88mm go from some 35 m to 38 m over 9500 m, this would give a downward curve. The obvious check comparison is 3.7 in HAA or 90 mm AA RT/FT, it'll be a couple of months before I can get my hands on the former (for surface to surface fire) and I haven't a clue where to find the latter.

 

Incidentally the 25 pr RT data quoted is not entirely correct, it looks as if its Chg 3, whereas Chg Super would be a better match to 88mm, I have 25 pr 50%s down to 1000 m.  A complete list of 25 pr RTs can be found on the 25 pr page of my web site, there's quite a lot of them!  I've also got a recollection that the chg 3 50% were subsequently updated in one of the editions after 1939 (something I stumbled on when doing the graph for my web site).  Just for the record and to correct mistakes, the 25 pr Chg Super 50% at each 1000m from 1000m to 12000m are (including the 88mm extreme points in brackets): 30 [69], 30, 40, 50, 50, 60, 60, 70, 70, 80 [75], 90, 90.  The progression is obvious.  I hope this makes my point about 88mm being weird a bit clearer.

 

However, after some digging I've found one instance that's a similar pattern - 175mm Chg 1 Green, max rg 15km, 50% @ 1000m  46m, @ 10,000m 46m, and it actually dips in between!  However this is a far heavier shell and far lower MV than 88mm, and Chg 1 White goes from 92m to 230m for the same ranges!  I've also come across people who have regarded the PE data for 175mm with some suspicion (putting it mildly).

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Yes, I see there was a revised set of range tables issued on 30th of Sept, 1942 and yet another revision on 28th April 1943. Apparently these folks were having issues trying to nail down the ballistics of the 25-pdr. So many revisions in such a short period of time is never a good sign. But I can partly see your implied point, and this may cast doubts upon the reliability of any Range Tables coming out of the UK during this period.

 

Anyway, this is a comparison the 1939 RTs to the 1943 Revisions – 25-pdr HE Streamline, Charge-3. We are still seeing the same trend. It is still a relatively flat curve and very low rates of change for the length of the 50% Zone at lower ranges. And again, this transitions into a much higher rate of change in the length of the 50% Zone for the longer ranged shoots. Still no real inconsistencies to be noted between these curves and the 88mm spgr dispersion zone curve – i.e. relatively flat transition to steep. Unfortunately I still am not seeing any evidence presented thus far that suggest there is anything unusual with the 88mm spgr curve.

 

FIG: Comparison of 1939 RTs to the 1943 Revisions – 25-pdr HE Streamline, Charge-3

 

Regarding the 25-pdr HE streamline supercharge tables being a better comparison to 88mm spgr than the 25-pdr HE fired at charge-3 – the 50% Zones are in essence the same for both charge-3 and supercharge. At least according to the 1943 Revisions The only change is in the additional range added by the supercharge. Below are curves showing the 1943 revisions of charge-3. I have overlain the 50% Zones for the supercharge. The breaks are all identical up to the point where charge-3 “runs out of range”. (The black lines are the supercharge zones, the yellow diamonds are the charge-3 zones). Again, there isn’t any real evidence here regarding the 88mm spgr dispersion curves being unusual.

 

FIG: Comparison 1943 Revisions – 25-pdr HE Streamline, Charge-3 & Supercharge

 

I think what this exercise does show is that 88mm spgr. is much more consistent than 25-pdr Streamline HE -- that is assuming the UK tables can be trusted. Moreover the Length of the 88mm spgr’s 50% zone remains relatively constant out to much greater ranges. It is also much more accurate than the 25-pdr at longer ranges. Clearly 25-pdr holds a bit of an advantage at ranges out to about 5000-yrds, after which its accuracy starts to decrease rapidly. The 88mm spgr is fairly steady at over twice this range.

 

Regards

JD

Edited July 6, 2006 by jwduquette1

[Mobius]

could this be modeled with my naval ballistics program?