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The QF 25 pounder as 1

 
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The QF 25 pounder as 1 - 8/4/2008 4:59:09 AM   
Central Blue

 

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Joined: 8/20/2004
Status: offline 		ever wonder about the 25 pounder and its AP rating of 165 - as seen in bio-ed?

I was browsing this excellent site today and it seems that the Brits did research on the comparative effects of artillery rounds, and rated the 25 pounder as "1"

I was reminded of Curtis Lemay's work on warships and the Warspite as his "1."

Well, much of the math is too advanced for me. But within my sphere of confidence, if not competence, was to create a simple formula to arrive at an AP of 165 based on a presumed "normal" ROF of 3 rounds per minute for the 25 pounder, and a bursting charge of .8164 KG for the standard HE round as described at the site linked above.

To arrive at 165 I multiplied .8164 * 67.36 * 3 (presumed normal ROF per minute). In my world it added up to 165.

With this formula, and info for normal rate of fire and weight of bursting charge, I was able to come up with some of the following raw ratings for a few pieces...

BL 5.5 inch AP 367
M115 8 inch AP 556

Those that don't care about outliers with low bursting charges - like the 4.5 inch - could work a similar formula off total shell weight. The charge weight is not always easy to come by.



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USS St. Louis firing on Guam, July 1944. The Cardinals and Browns faced each other in the World Series that year
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RE: The QF 25 pounder as 1 - 8/4/2008 5:15:17 AM   
ColinWright

 

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RE: The QF 25 pounder as 1 - 8/5/2008 12:46:51 AM   
rhinobones

 

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quote:

ORIGINAL: Central Blue
To arrive at 165 I multiplied . . .


Curious . . . how does your computational method hold up when you apply it to IX Century artillery?

Regards, RhinoBones

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RE: The QF 25 pounder as 1 - 8/5/2008 1:51:01 AM   
Central Blue

 

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Joined: 8/20/2004
Status: offline 		in the IX century they were probably more concerned with ROF and weight of shot, if they thought about such things at all. I don't think anyone had gunpowder then. I never gamed that era.

I am working on a spreadsheet that considers shell weight or bursting charge. If you wanted to use shell weight and sustained rate of fire for 19th century cannon that are in the COW db, then I suppose it would work. There is always something to be said for filling the air with flying metal, you just wouldn't have as much range.

Should the 24 lb RML have a higher AP than your typical 81 mm mortar that can sustain ROF between 15 and 18 rounds per minute? Probably not. The typical weight for an 81mm mortar projectile runs from 7 to 10 pounds, so it is putting considerably more flying metal in the air than could Horatio Hornblower with his best gunners on the 24 pounder -- unless they can sustain 4 rounds per minute.

The interesting thing is finding "1" in the DB. I don't think it's the QF 25 pounder. But I will be posting my spreadsheet later, if I don't revise it entirely. I always thought the shell weight was kilograms, but I see that the 24 pounder is indeed shell weight 24 and the 12 pounder -- 12.

"1" might not be in the DB at all, but I do have to wonder how the original values were arrived at.



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USS St. Louis firing on Guam, July 1944. The Cardinals and Browns faced each other in the World Series that year

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RE: The QF 25 pounder as 1 - 8/5/2008 2:20:45 AM   
Central Blue

 

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Joined: 8/20/2004
Status: offline 		I probably didn't answer the question that was asked...

If the 24 pound RML causes AP damage at 48 with sustained ROF of 1 round per minute... The QF 25 pounder is worth 150 at 3 rpm, and the M1 81mm mortar and its shell are worth 206 at 15 rpm.

Maybe the 24 pound RML is "1" if you prefer to go by shell weight and ROF.

_____________________________

USS St. Louis firing on Guam, July 1944. The Cardinals and Browns faced each other in the World Series that year

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RE: The QF 25 pounder as 1 - 8/5/2008 3:09:15 PM   
Central Blue

 

Posts: 695
Joined: 8/20/2004
Status: offline 		if I have done this correctly, there should be a zipped spreadsheet attached that shows the ratings for various weapons if the 24 pounder RML and it's AP of 48 were "1"

In this case I converted the 24 number to kilograms to be consisted with data already entered for other systems.

This system does seem to be a little kinder to mortars than what is currently in the game. Even the 2 inch is worth carrying along. And as I read it, the standard load was twelve rounds of HE. Given an 8 rpm firing rate, the platoon could put 12 kilos of metal in the air in 90 seconds if they needed to.

I don't know if the 24 RML should be "1." You may have your own ideas. If you want to make the 2" your gold standard, divide the AP by the weight, and then divide that by the ROF to find your modifier. But I must warn you that if you do, your QF 25 will only be worth 64.



Attachment (1)

_____________________________

USS St. Louis firing on Guam, July 1944. The Cardinals and Browns faced each other in the World Series that year

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RE: The QF 25 pounder as 1 - 8/6/2008 4:24:25 PM   
Central Blue

 

Posts: 695
Joined: 8/20/2004
Status: offline 		I think that the 105 makes the best "1". The AP on the QF 25 gets knocked down to 97, but at least you can bump its weight to 11 from 9. I think this scale also works pretty well for the direct fire weapons like AT and tank guns as for example the QF17, QF20, and 105 L7 on the Centurion marks where there is currently a wide discrepancy that could only be explained by change in loading rate rather than discrepancy between shell weights.

If you prefer gaudier numbers, then work the formula off the AP rating of 260 for the 150's, or 43*12.1*.5

I haven't done all of the research, but I suspect that the 100mm and 104mm (for example) would get knocked into a better scale of AP if someone had the data on shell weight and ROF to plug in.

Attachment (1)

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USS St. Louis firing on Guam, July 1944. The Cardinals and Browns faced each other in the World Series that year

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