Shell Weight Corrections

[maxspee]

I've been looking at the shell weights in the gun data files, and believe a few of the upper calibres aren't good projections of shell weight (and in the instance of 18" not historical)

For gun calibres 4-16" they are broadly historical (the 8" guns fractionally lighter than I'd expect, although the French Heavy cruisers 8" shell was heavier than this value so I suppose its not terribly inaccurate)

After 16" the values, in my opinion get a little wonky.

We know Yamato's shell weight was 3220lb, and the british 18" MK1 was 3320lb so 3500lb seems off, I would suggest the average of the two 3270lb

Additionally 3000lb for 17" guns is too great an increase from the 16"

Given the exponential relationship between shell weight and calibre the 19 and 20" values are vastly under what they ought to be all things equal.

Using the following values (note the amended 18" shell weight) I produced the polynomial formula to derive shell weight.

Gun Calibre Shell Weight

4 32.00

5 63.00

6 108.00

7 172.00

8 276.00

9 365.00

10 500.00

11 666.00

12 864.00

13 1200.00

14 1372.00

15 1688.00

16 2048.00

18 3270.00


The formula is as follows: y = 6.10889497E-03x6 - 3.66173478E-01x5 + 8.76223990E+00x4 - 1.06216063E+02x3 + 6.95345263E+02x2 - 2.29101120E+03x + 2.97684203E+03

where x is calibre and y shell weight.

This created a very good fit vs the games values for the other "historic" shell weight (plus my adjustment to the 18")



Using this formula I was able to derive the following shell weights for 17", 19" and 20":

17 2516

19 4552

20 6739

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[brygun]

Just a small comment that the weight to carry needs to include the not just the shells but the storage spacing, machinery if any, crew to pass or operate machinery, safety doors and the barbette armor.

AFAIK 2" to 4" shells are easily passed by hand as one piece ammuntion. 5" passed by hand is iffy one piece though doable 2 piece. 6" two piece (150 mm) is possible but Id want to check on that. 7" and above defininetly needs machinery. Not sure where 8 or 9" machine handled one piece aummunition is. Larger calibers often being multiple pieces like the Iowa's with the huge shell and 3 powder bags for propellant.

A curve fit ought to break out at least the manhandled ammunition as a different environment.

There is a little bit of economy of scale as each barrel needs a lift (or gang of people) to go from the magazine levels to the gun but only one whether there is 50, 90, 100 or 150 shells down below.