1925 Naval Artillery Ballistics

[Kaiser Kirk]

Part of having custom Naval Artillery and running battles is trying to estimate the penetration of the guns at that range and angle. For angles, I simply use the physical thickness at that angle.

I also roll for section of ship bow/citadel/stern per the ship's freeboard allocation.
I also roll for height of hit - from below water to freeboard. There are superstructure hits in the charts as well.

For the Penetration, pregame I used 'BigGun'- a Dos Program - to estimate starting Parthian Guns.
I could use this in DosBos, it makes a nice text file :)

I now use Logi's Ballistics tool
Logi's Tools

Part of that tool is trying to find the right coefficient for the Belt and Deck armors.

Trying to find appropriate numbers for these I have been using NavWeaps charts for shell penetrations for that era.

The 1925 Naval Artillery caused a problem - few new guns of this Era, and there are no @1930 test results on NavWeaps for them.

There are 1935 British Estimates.
And some German charts for their Guns
then there are the 1942 USN Empirical Formula

Interestingly there are even some guns with both 1935 AND 1942 estimates...
And the USN ones have more penetration.

Various sources I've read indicate the final USN shells were better penetrators, so the 1942 data might be right for that, and not earlier shells.

1. So I am proposing to use the 1935 British Estimates as the basis. I evaluated the German numbers from Bismarck as well.

From that I come up with :
Option 3 – Average the averages       
Belt    418.167   
Deck    343.778   


2. The attached spreadsheet I took the NavWeaps Charts for 14/45, 15/42 and German 15/48.
For each range they listed a penetration for, I tried to find the appropriate coefficient.
I then averaged the values found to get the result.

Barring objections, I will use these figures for future conflicts.

I will also be using them (or likely rounded) for the Parthian guns, to estimate
what armor I need to stand up to my own guns.

3. IF we introduce another Naval Artillery Tech, then I will do the same process with the
1942 USN Empirical numbers to produce coefficients for that.

[Kaiser Kirk]

I guess
Option 4 ) Average 1935 and 1942
Option 5 ) Just use the higher penetration values of 1942

[Kaiser Kirk]

I'm starting to look at the 1942 averages, that may take longer.

What is really standing out to me is I used the 1935 numbers for Parthia's naval artillery,
not only is my 365/50 a heck of a gun, and I should have used that instead of the 390/46 on Wirozag but none of my guns have worthwhile deck penetration.

Now, considering the Brits did not expect the 15/42, which is lower MV, higher shell weight - should be a good deck penetrator... to reach 4"/102mm until 28,000yd / 25600m.
Contrast that with the USN formula that expects 121mm at 25,000 yards - 20% more at lesser range than the Brits

Push out to 29,500yd/26,970m and you reach 5"/127mm by the British method.
Meanwhile the USN at 30,000yd/27,432m is at 5.7" / 145mm - 14% more.


There's a large tonnage difference there in potential deck armor savings. 
If I can give an AC 105mm deck armor and be 'proof' out to 25km, that sounds like a deal, because I expect few to no hits past that. Granted there's still the bomb threat... but I am looking at a 25-35mm upper bomb deck,
which could let me drop the main deck to ~90mm. Still proof vs. 15/42 out until ~24,000yds.

Also, I may as well keep the high MV for belt penetrations if deck never really gets high enough.
Granted after ~16km you pass the 50/50 belt/deck hit range.

But it's looking like you can really only hope for critical damage inside that range.
Or mission kill with lots of hits, then close in. Which was the Brit concept with the KGV.

It's like I remember reading about pre-WWI tests on British AP shells and they were not passing more than 9" armor on shallow oblique ~20% hits... which made me think of the 9" armor on the Splendid Cats and wonder if there was a link. Of course the Germans came out with shells that did pass and explode....so that was an issue.

[Kaiser Kirk]

Oh, and I am thinking when I finish tinkering with the numbers,
I should post some "standard guns" with their penetrations for folks enjoyment.

[Kaiser Kirk]

This Table models the Navalism Gun Research Chart for the 1935 values.
When I figure the 1942 USN Empirical coefficients, I will post examples of both for comparison.

The centroid of each bore range, with default shell weight at 50 calibers is used.
Since the 18" range has no upper limit, I used 19" aka 483mm.
For smaller guns, 250, 200 and 150 are used as informative examples
As the ME is fixed for each bore range, large bores with heavier shells will have the same ME, giving less MV and better deck penetration but less belt penetration
Smaller Bores will have higher MV & Belt Pen, but less Deck pen.

The Splinter is the 1/6th shell diameter splinters will hit, allowing above-deck hits to effect below-deck systems even if the shell detonated above the deck.

								Coefficients :
								Belt :	418.167
Normalized for 15"/42 879kg 749mps 6chr values								Deck :	343.778
				10km	10km	15km	15km	20km	20km	25km	25km	30km	30km
Naval Artillery	Shell (KG)	MV	Splinter Pen	Belt	Deck	Belt	Deck	Belt	Deck	Belt	Deck	Belt	Deck
483L50	1647	699	81	556	16	447	38	363	75	298	131	244	217
436L50	1214	755	73	562	12	444	30	356	60	291	103	242	166
386L50	843	810	64	540	10	415	24	326	48	262	83	217	132
336L50	556	850 (893*)	56	478	8	355	20	269	40	212	70	173	113
283L50	332	850 (977*)	47	358	7	252	18	183	37	140	66	111	108
250L50	229	850 (906*)	42	287	6	194	17	136	36	101	65	79	106
200L50	117	850 (907*)	33	186	6	115	16	75	34	53	63	46	79
150L50	49	900 (910*)	25	100	5	53	14	31	33

*Normally I cap MV at 850 for large guns and 900 for small, as the expected bore life got terribly short over that.
In real life you see these HV guns derated and fired at lesser velocities to extend the barrel life.

[Kaiser Kirk]

The reason I'm bothering with this is that I want to ensure all of us have access to the same information.

If anyone is reading all this and thinking "He's got it all wrong ! We should do it X way".
Well, come explain what X way is.

Choosing to stick to Royal Navy preferentially ensures that the statistics generated fro our custom guns is based on the same data that Jefgte's choices of real world guns is based on.
That seems fair. 

I am well aware that others do not seem to try 'fine tune' their guns/armor choices,
but I feel it is important that
1) HOW one would do this is transparent
2) Everyone knows where the tools to do it are
3) HOW exactly I'm getting numbers for combats.

I would have done this long ago, I have long had a excel sheet for Parthian naval art,
and planned on making a 'easier to use' version for all...
 but instead wound up doing it on a rushed basis for conflicts.

[Kaiser Kirk]

This is meant to be informative as to the expected capabilities of the 1925 Artillery.

Please note that I did not make this chart, it's just the standard we all got with Navalism.

The Research chart is arranged in ranges such as 410mm to 361mm,
and so I used the midpoint of each range.

The heaviest shell available  was used.
For example, a 386mm gun is allowed to use a 60 caliber shell by the 1925 Tech.
That shell is 871.85, but is allowed to be 20% overweight, which makes it 1046.22.

IT is important to note that some Bore size/shell size combos result in low MV and
lesser performance.

The following table uses the coefficients outlined above, and the Naval Artillery tool to
calculate ME and MV for the various guns.

On the Belt armor numbers, it is important to note that this is at a 'right' or 90 degree angle for maximum penetration. 

In real life, Navies presumed fire would be at an angle, and based IZs on that assumption. So the USN used 60 instead of 90, which greatly increased how effective the Armor is.

Many of us use inclined belts of various sorts, which also is not accounted for.

On the Deck Armor, there is less variability, I suppose pitch/roll could change angles, but that is far to complex for me to consider.

In real life, guns with too high a MV stripped their bores quickly, and often had high dispersion, making long range fire inaccurate. Frequently this led to the guns being de-rated in service to address these problems. The maximum MV tolerated seemed to have been higher for smaller guns.

For N7, when I run battles, I cap heavy artillery at 850mps and lighter artillery at 900mps.
While there is argument for reducing it further, I figure since players can design their own guns, they can choose the MV they want.

This can be seen in the 231 example, where the /60 and /55 are reduced to 850mps, while the /50 is 813. This suggests that barrels from 55-60cal waste weight.
Note that the 181 with heavy shell is beyond hand loading weights. A turret is recommended.



                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               

1925 Naval Artillery Tech Values			211+ MV	Capped 850		Belt :	418.17		Deck	343.78
			210- MV	Capped 900				<====  >50% belt hits		>50% deck hits===>
Normalized for 15"/42 879kg 749mps 6chr values	Normalized for 15"/42 879kg 749mps 6chr values				10km	10km	15km	15km	20km	20km	25km	25km	30km	30km
Classification	Naval Artillery	20% over std Shell (Kg)	ME (adjusted)	Heavy shell MV	Belt	Deck	Belt	Deck	Belt	Deck	Belt	Deck	Belt	Deck
> 460mm	485L50	2005.812	11450	694	713	18.6	594	45	497	87	419	150	351	242
	485L45	2005.812	(10305)	659	641	20.6	532	50.1	443	97.8	368	171	315	254
460mm to 411mm	436L55	1485.792	9500	735	711	15.3	585	37.3	485	72.1	407	123	345	196
	436L50	1485.792	(8636)	701	646	16.9	530	41.1	438	80	365	138	304	225
	436L45	1485.792	(7773)	665	580	18.8	474	45.9	390	90	320	158	275	230
410mm to 361mm	386L60	1046.22	7860	797	720	11.9	581	29.1	475	56.5	396	96.3	336	151
	386L55	1046.22	(7205)	763	659	13	532	31.8	434	61.9	360	106	304	169
	386L50	1046.22	(6550)	727	598	14.3	481	35.2	392	68.6	324	119	269	192
360mm to 311mm	336L60	690.048	6300	878->850	669	9.36	524	23.1	418	45.2	341	77.7	286	122
	336L55	690.048	(5775)	841	655	9.54	513	23.6	409	46.2	334	79.5	280	125
	336L50	690.048	(5250)	802	595	10.5	466	26	371	51	303	88	253	140
310mm to 256mm	281L60	403.62	4500	970->850	507	8.12	380	20.5	292	40.9	231	71.4	190	114
	281L55	403.62	(4125)	929->850	507	8.12	380	20.5	292	40.9	231	71.4	190	114
	281L50	403.62	(3750)	886->850	507	8.12	380	20.5	292	40.9	231	71.4	190	114
255mm and less	231L60	224.232	(2106.17)	891->850	368	7	259	18.2	189	37.4	144	66.7	115	108
	231L55	224.232	(1930.65)	853->850	368	7	259	18.2	189	37.4	144	66.7	115	108
	231L50	224.232	(1755.14)	813	335	7.66	237	19.9	173	41	132	73.4	104	121
255mm and less	181L60	107.868	(1013.19)	891	258	5.43	167	14.8	114	31.5	82.4	57.6	63.6	94.5
	181L55	107.868	(928.76)	853	237	5.91	153	16.1	104	34.4	75.5	63.2	60.7	95.1
	181L50	107.868	(844.33)	813	215	6.5	139	17.7	94.7	38	68.1	70.4	59.4	90.1
255mm and less	131L60	40.896	(384.12)	891	132	4.58	73.3	13.6	44.5	30.8	29.4	58.6
	131L55	40.896	(352.11)	853	121	4.99	67.3	14.8	40.7	33.7	28.7	57.3
	131L50	40.896	(320.1)	813	110	5.5	61.2	16.3	36.8	37.3	28.5	54.6
255mm and less	81L60	9.672	(90.81)	891	37.5	4.11	15.2	14.6	8.86	27
	81L55	9.672	(83.24)	853	34.4	4.48	13.8	15.9	8.91	26.1
	81L50	9.672	(75.67)	813	31.3	4.93	12.4	17.6