Range and Penetration Table for the 38 cm SK C/34

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José M. Rico
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Range and Penetration Table for the 38 cm SK C/34

Post by José M. Rico » Mon May 05, 2008 9:12 pm

The following data has been extracted from the official German projectile curves found in document "Awa A IA100/40 g.Kdos Unterlagen und Richtlinien zur Bestimmung der Hauptkampfentfernung und der Geschoßwahl" which were kindly provided to us by William J. Jurens.

Range - Striking Velocity - Armour Penetration
10,000 meters - 642 m/s -
15,000 meters - 569 m/s -
17,000 meters - 544 m/s - 460 mm (side)
18,000 meters - 532 m/s - 442 mm (side)
20,000 meters - 510 m/s - 412 mm (side)
25,000 meters - 474 m/s - 335 mm (side), 100 mm (deck)
30,000 meters - 459 m/s - 275 mm (side), 126 mm (deck)
35,000 meters - 461 m/s - 228 mm (side), 165 mm (deck)

Click on the link below to see the complete range and penetration table for the 38 cm SK C/34 gun firing a 38 cm Psgr. L/4,4 Armour Piercing shell.

http://www.kbismarck.com/38cm.html

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Re: Range and Penetration Table for the 38 cm SK C/34

Post by dunmunro » Tue May 06, 2008 12:54 am

Here's a set of penetration tables for most European theatre BB guns:

http://www.sfu.ca/~dmunro/BB_Gun_pen.html

I thought I would repost here to make it convenient to compare with the official German 38cm tables. NAaB 1.0 uses Nathan Okun's armour penetration formulas which are based upon empirical USN data with input from numerous other national sources. As you can see there is very good agreement.

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One remark on the link

Post by Serg » Wed May 07, 2008 9:47 am

I familiar with such definitions of statistic science as probable error, mean deviation, standard deviation etc. But I want to be precise about "dispersion". What does that word represent in this case, can someone provide an explanation? (unfortunately, I do not really read German)
regards,
serg

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Re: Range and Penetration Table for the 38 cm SK C/34

Post by lwd » Wed May 07, 2008 10:54 am

Do you have an example of where it is used. Also remember even if it has a precise technical definition it may have a looser definition in common usage. As used in the table I'm not sure exactly what it means. Obviously a measure of variation in shot to shot errors. The fact that it's not a linear function of range makes me curious. It could be total error or range error. But whether it's the total size of the shot group or the radius or diameter of the 50% circle or a standard deviation I'm not sure.

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Re: Range and Penetration Table for the 38 cm SK C/34

Post by José M. Rico » Wed May 07, 2008 1:50 pm

I'm not sure either.

50%ige Längenstreuung /50 [Dm] = Dispersion Zone, longitudinal scatter

This was previously discussed here: viewtopic.php?t=613

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Re: Range and Penetration Table for the 38 cm SK C/34

Post by lwd » Wed May 07, 2008 3:07 pm

Now I'm getting really confused. The chart at the top says dispersion at 15,000 meters is 50.4 meters but the refeance you pointed to says:
50% Zone at 15000meters range has a length of about 140meters
So the two numbers seam to indicate different things.

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Re: Range and Penetration Table for the 38 cm SK C/34

Post by José M. Rico » Wed May 07, 2008 3:22 pm

lwd,

I think I made a mistake extrapolating those figures from the curves. I will check that again, but note that the curves of the thread I linked to are supposedly from a British 38,1 cm gun firing a 875-kg shell and not from the German 38 cm SK C/34. I just added that link as an example.

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Re: Range and Penetration Table for the 38 cm SK C/34

Post by lwd » Wed May 07, 2008 5:24 pm

Ok that may explain it because I just saw the gun size and didn't look closely at the details. Still the British 15" gun had a reputation of being pretty accurate I thought.

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Re: Range and Penetration Table for the 38 cm SK C/34

Post by José M. Rico » Thu May 08, 2008 6:12 pm

lwd wrote:The chart at the top says dispersion at 15,000 meters is 50.4 meters
I have just revised and corrected the chart for the 38 cm SK C/34 and the correct figure at 15,000 meters as read from the curves is 100 meters.

I have also added "Sweep Zone" figures to the chart for a 10-meter high x 30-meter wide target.

Updated chart here:
http://www.kbismarck.com/38cm.html

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Re: Range and Penetration Table for the 38 cm SK C/34

Post by lwd » Thu May 08, 2008 7:41 pm

That would be consistent with the 50m being read as + or - 50 meters for the 50% dispersion interval.

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Re: Range and Penetration Table for the 38 cm SK C/34

Post by corvette1250 » Tue Jun 02, 2009 8:01 pm

can anyone refer me to information reference to speculated location of the one 'kill" round from bismarck to hood? i am interested, if possible, to obtain enough info for a 3d reference on computer. :shock:

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Re: Range and Penetration Table for the 38 cm SK C/34

Post by Bgile » Tue Jun 02, 2009 8:45 pm

corvette1250 wrote:can anyone refer me to information reference to speculated location of the one 'kill" round from bismarck to hood? i am interested, if possible, to obtain enough info for a 3d reference on computer. :shock:
I think some of the best information is on the hms Hood organization web site.

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Re: Range and Penetration Table for the 38 cm SK C/34

Post by lwd » Wed Jun 03, 2009 1:03 pm


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Re: Range and Penetration Table for the 38 cm SK C/34

Post by nathanokun » Mon Oct 26, 2009 2:18 am

Hit on HOOD: The shell could penetrate the rather thin layers of spaced armor directly into the aft magazine if the fuze delay was long enough (the German base fuze of the time for its 38cm APC projectile was 0.035-second nominal average delay, giving it a distance of about 53 feet at 1500 ft/sec average velocity through the ship). The HOOD's armor design was for use against WWI-era non-delay base fuzes that only went a few feet inboard before exploding and the inner plating could stop such pieces -- modern delay-action-fuzed APC shells made this very vulnerable!! This was actually rather a small target, though, compared to the entire ship. However, there was only about 1" of HT (ship construction) steel between the aft engine room and the 4" AA gun magazine directly in front of the main aft magazines. Thus a hit in the aft engine room or 4" magazine was essentially the same as a hit in the aft main magazine, since the 38cm APC shell could easily put its fragments through plating that thin unless very far away from the explosion. Now the target is MUCH larger and much more likely. Blow up the 4" magazine, or at least part of it, and the main magazine, which is similarly separated from the 4" magazine by thin plating, would go off, too. Bye bye HOOD!!

Nathan Okun

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Re: Range and Penetration Table for the 38 cm SK C/34

Post by nathanokun » Mon Oct 26, 2009 5:07 am

This assumes KC n/A ("Krupp Cemented New Type" -- thick plate first used in SCHARNHORST) armor, with its 41% total face layer (59% unhardened back), straight-line hardness drop from the face behind the thin super-hard Cemented (carburized) layer to the back (most other face-hardened KC-type armors, including previous Krupp KC armor, had the hardness drop off much more slowly until near the back layer and then drop off very fast in a ski-slope curve), and somewhat high back hardness. Cemented layer 650-700 Brinell (very high hardness as with all Krupp KC armor; most other manufacturers used about 600-650 Brinell, while British WWII Cemented Armor (CA) reduced this to about 600 Brinell maximum to reduce brittleness, with some success) for about 2.5-3.5cm depth, then 500-550 Brinell maximum hadness decremental face (similar to most other non-British WWII KC-type armors; dropping in a straight line with depth to the 240-250 Brinell back layer hardness at 59% depth (average, but quite reliable) from the surface of the plate.

Many foreign plates used the original Krupp KC -- renamed by Krupp as "KC Old Type" (KC a/A) when KC n/A came out -- face layer thickness of 33-35%. British WWII CA reduced this to about 25%, while the US Class "A" armor of WWII increased this to 55% (average). Each concept had its theoretical reasons, but I seem to be the only one to figure out the rule: Thicker faces give higher "Scaling" effects (bigger shells penetrate proportionately thicker armor at a lower striking velocity, all else being equal, so the EFFECTIVE armor quality goes DOWN with increasing SHELL SIZE, even when the armor steel quality in tensile/brittleness tests is identical for all plates) than thinner faces do, with this giving the advantage to thick faces for thin plates for use against small projectiles and thin faces for thick plate for use against large projectiles, assuming a minimum face thickness to damage the projectile nose in the first place, of course. My FACEHARD program at www.navweaps.com has a table for this built-in.

British CA plate is thus better against big shells, while US Class "A" armor is noticable inferior against big shells, but the best for cruiser-size armor plates. All are noticably better than all thicknesses of WWI-era armor by the same manufacturers due to higher quality steel used (my actual "Armor Quality" factor), so most manufactuers did not notice that this widely varied AMOUNT of improvement against different projectile sizes due to scaling had a pattern until I could compare all of the varying face-hardened armor types against each other on a "level playing field" using calibrated shells (shell damage resistance varied a lot and masked much of the plate quality/scaling effects). Interestingly, Italian WWII Terni KC had such a near-ideal scaled face thickness -- the face layer was almost the same thickness for all plates from the thinnest circa 12.5cm (circa 50% of the plate was face) to the thickest at 38cm (only about 20% of the plate was face), so the scaling effect optimization is built-in. KC n/A is thus somewhat on the too-thick-face side against large shells, but the effect is much smaller than with US Class "A".

Nathan Okun

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