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The Brit 15 inch


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#1 W. Clark

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Posted 10 July 2018 - 01:46 AM

I'd like to ask just what the Brit 15 inch on the RN gunnery chart represents. Does it apply as is to the RN for the period 1939 to 1945? Or is it taking improved shells into consideration that did not come into service until 1942 or there about? I'm being told that the 15 inch should not penetrate BA armor up to 18,000 yards in 1940. That instead its penetration should be reduced to BB by a range band or two; say beyond 15,000 yards.



#2 Cpt M

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Posted 13 July 2018 - 08:13 PM

I'd like to ask just what the Brit 15 inch on the RN gunnery chart represents. Does it apply as is to the RN for the period 1939 to 1945? Or is it taking improved shells into consideration that did not come into service until 1942 or there about? I'm being told that the 15 inch should not penetrate BA armor up to 18,000 yards in 1940. That instead its penetration should be reduced to BB by a range band or two; say beyond 15,000 yards.

 

According to John Campbell, the RN adopted in 1938 a new, slightly heavier APC shell (the APC Mk XIIIa(6crh)).  These new shells were limited to Warspite, Valiant, Queen Elizabeth and Renown (ships with the upgraded Mk I/N or Mk I/N* turrets).   The older unmodified turrets' shell handling equipment were unable to handle these shells due to their longer length.  To remedy this, an additional shell was issued (the APC Mk XIIIb(4crh)) which had the same shell body and cap but with a 4crh windscreen.  These were issued concurrent with the APC Mk XIIIa(6crh) shells.  In 1940, Barham's turrets were upgraded to handle the 6crh shells and the remaining unmodified 15" turrets were upgraded from late 1941 to mid 1943 (which ships and when is unknown, but Raven undoubtedly has that information).  According to Nathan Okun, ALL of the 15" APC shells issued during WWII had similar armor penetration performance.  Which makes sense; the only difference between the APC Mk XIIIa and APC Mk XIIIb being the windscreen, the body of the shell being the same.  The only performance difference between the modified and unmodified turrets was range.  The unmodified turrets (with a 20 degree maximum elevation) had a shorter maximum range than the modified turrets (with a 30 degree maximum elevation).  To remedy the range shortfall, the RN developed for the unmodified ships a "Super Charge" which was the maximum propellant charge that the guns could safely handle.  However, according to the RN's records, no ship ever used this "Super Charge" in combat (in fact, its doubtful they were ever issued in any quantity for use due to problems with excessive barrel wear and mount safety).  The only recorded use of the "Super Charge" was by the coastal artillery. 
 
The only shells in frontline use during WWII would be the APC Mk XVIIa and APC Mk XVIIIb (all the prior shells, the APC Mk Ia(4crh), APC Mk IIIa(4crh) Greenboy, APC Mk Va(4crh), and APC Mk XIIa(4crh) had been retired). 
 
So in game terms, there would be no difference in armor penetration between the unmodified and modified 15" ships.  The only difference would be the maximum range, which is already indicated on the RN CRT.  Also, we can safely disregard the "Super Charges" given their limited availability (and the lack of evidence supporting their use in combat).  As for the penetration, in comparing the CRT to Nathan Okun's tables, the CRT is consistent with Okun's results (after adjusting for service results verses theoretical results).  Given all the above, I can see no reason to modify the current RN CRT.  

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#3 Cpt M

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Posted 14 July 2018 - 11:32 AM

Correction:

 

"The only shells in frontline use during WWII would be the APC Mk XIIIa and APC Mk XIIIb (all the prior shells, the APC Mk Ia(4crh), APC Mk IIIa(4crh) Greenboy, APC Mk Va(4crh), and APC Mk XIIa(4crh) had been retired)." 

 

 

Never post before coffee!   :) 



#4 W. Clark

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Posted 17 July 2018 - 12:28 PM

Thank you. It is my experience with GQ3.3 that when ever the rules are questioned they have always been vindicated when all the evidence is in. That is why I questioned the argument and your reply confirms my belief that the rules had it right.



#5 Richard Pelvin

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Posted 26 March 2020 - 10:19 PM

Reopening this topic, you state in your reply:

 

'So in game terms, there would be no difference in armor penetration between the unmodified and modified 15" ships.  The only difference would be the maximum range, which is already indicated on the RN CRT.'

 

I'm cannot find anything in the CRT which distinguishes between the Mk I mounting for the British 15 inch gun and the refurbished Mk I(N) mountings as on WARSPITE, QE, VALIANT, RENOWN and VANGUARD. The range difference is tactically important as shown by the performance of WARSPITE's guns vis a vis MALAYA's at Calabria.

 

The CRT appears to refer to the Mk I (N).

 

In the same vein, I presume the 6 inch column refers to the more modern gun on the light cruisers of the 30s and 40s, not those on the C, D and E classes, EAGLE and older battleship secondaries.

 

Ric



#6 Dave Franklin

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Posted 28 March 2020 - 12:55 PM

Ric,

 

If you look on the Royal Navy Gunfire CRT, in the [Day] 24,000 yard row between the 15" and 14" columns, there is a little box that says ' Old 15" '.  That is to indicate the British BBs which had not had their 15" gun elevation increased have a maximum range of 24,000 yards.  Unfortunately, the meaning for that little box, and the ships it pertains to, are not called out.

 

WRT the British 6" guns, in Defending the Malay Barrier, The ABDA Campaign, we added Optional Rule 3.12, which states "Due to several factors (e.g. gun and gun mount design, shell handling and ammo supply restrictions, fire control issues, etc.) the following old Commonwealth and USN CLs armed with 6” guns should not be allowed to use GQ 3.3 Rapid Fire":

Commonwealth:
‘D’ class: HMS Danae, HMS Dragon, and HMS Durban
‘E’ class: HMS Emerald
USN:
Omaha class: USS Marblehead
 
You could certainly apply that to 'C' class cruisers as well.  I would need to do some investigation to see if I thought it should apply to the Queen Elizabeth and Royal Sovereign class BBs; however, it seems reasonable at first glance.
 
I hope that addresses your questions,
Dave


#7 Richard Pelvin

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Posted 29 March 2020 - 12:17 AM

Thanks very much, Dave. I missed the reference in the original CRT as we have always used the 1cm = 200 yards download. Happy with the 6 inch gun restriction but I feel there should also be a range penalty. An easy solution for that would be to adopt the same solution as for the unmodified 15 inch.

 

A column for the Brit 7.5 inch would also be useful.



#8 Richard Pelvin

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Posted 29 March 2020 - 12:24 AM

Further to the above, a closer has look has shown that the 1cm = 200 yd download also has the old 15 inch designation. My bad.

 

ric



#9 Dave Franklin

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Posted 29 March 2020 - 09:19 AM

WRT the British 7.5", I'm sure it wasn't included due to space restrictions on the chart, and the fact it would only apply to 3 ships (Hawkins class cruisers), and only 2 ships after May 1940.

 

You might note on the Italian Gunfire CRT, it combines the 7.5" (for ships, only found on San Giorgio) and the 6".  I can't really comment on this, other than to note it appears from a range perspective to be reasonable.  The NavWeaps pages for both the British and Italian 7.5" guns are not as comprehensive as others (e.g. there is no penetration data, or data on the bursting charge).  You could take the same approach with the British 7.5" (I would add the caveat that they cannot rapid fire, and would probably limit them to 21,000 yards max range).  The only other thing I personally might do is, referencing the Soviet Gunfire CRT's 7.1", I might say the British 7.5" should use the 8" Equivalent Damage Table, except the entry for "CA - CS" is x1.  I might even do the same for San Giorgio...

 

I ran into a similar issue doing an Operation Cerberus/Channel Dash game for the 9.2" guns of the South Foreland Battery.  I elected to use the 10"-9.4" from the Northern Navies Gunfire CRT.

 

Dave



#10 Richard Pelvin

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Posted 29 March 2020 - 10:51 PM

Thanks again, Dave. All very useful suggestions which give us something to work on.

 

Ric






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