Destroyers are quite maneuverable and SOP was turn ASAP to present the maximum amount of firepower to attacking aircraft.
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And against attack from ahead Bensons could use 4-5 x 20mm singles and usually one of the twin 40mm mount on the other hand Nizam only 3-5 x 20mm because its quad pom-pom and the only Bofors would have been wooded. One always can play with firing sectors.
Juha
Do you not understand that you need layered defence. Did the example of HMS Tiger whose 6in were deadly against aircraft but still needed 3in and Seact missiles not show this. That the USN with the 40mm and the 5in had the best combination going.I bet the boys from Fliegerkorps X would dispute your claim, but why did the USN need an effective CIWS when they had the mighty 5in/38 directed by the incomparable Mk33 and Mk 37? As for taking quite a toll that's not the case, as I have shown via Lundstrom.
And at the end the 4.7 stops firing and is useless against divebombers whatever you say this is the final fact.There's several things to consider; some aircraft flew lower and slower increasing the engagement envelope and, the RN introduced MT fuzes with longer time settings (45 versus 25 seconds) which combined with type 285 radar to push maximum range out several thousand yards and greatly increased accuracy of the resulting gunfire. As the altitude of the aircraft decreases, so does the differential between a 40deg gun and an ~80 deg gun and at higher elevations the accuracy of both the aircraft and the defensive gunfire decreases.
The first changes made were the replacement of the 0.5 with 20mm guns initially 4 then normally increased to 8 with twin mounts replacng singles. The TT were removed for the 4in, then replaced. Later the TT's were removed again and replaced with the 40mm.Last sentence above : Therefore propose to replace 4-in. H.A. in 'J' class and later and the 3-in. in 'E' to 'I' by the second set of T.T.s as opportunity occurs or by additional Oerlikons." The ships were designed with 2 x quintuple tubes so removing the 4in and replacing the tubes gets them back to their design configuration. The RN was always very cautious in terms of weight compensation to ensure adequate stability for their destroyers which had to operate in the bad weather prevalent in the Atlantic and Arctic oceans, along with the possibility of ice formation on the weather decks.
Where on earth did you get the RN saying the 40mm had the same effectve range of 1,700 yards.1700 yards = 5100 ft (they considered the Bofors to have the same effective range), but your point was about "harrassing fire" and this could be accomplished up to much higher altitudes - the engagement diagram actually shows a max altitude of ~7500 ft for the pom-pom but in any event at 2300fps (a typical MV of a worn gun in service) the max altitude was well above 10,000ft.
Which was nothing compared to other naviesThe fact is that ballast was required even with the original design configuration.
see above re 20mm being addedIf you look at the weight saved by replacing a 4.7in twin with a 4in twin and then removing the quad .5in mounts, it almost exactly balances the weight added by the 6 x 40mm mounts and the additional radar equipment.
I admit I don't get this statement can you explainThe Akizukis were more akin to an RN C class light cruiser than a destroyer but if the IJN had placed an emphasis on destroyer AA firepower they could have fitted the 5in/40 twin onto their fleet destroyers - but they didn't.
I have no idea but would assume they had a basic system similar to the US DE'sIt looks to me that the Matsus didn't have an AA FC system which the Hunt class did.
Well you have failed to convince anyone.I have been arguing that the treaty limited RN destroyers with the 4.7in twin represented a compromise between topweight, AA firepower and surface firepower and the lower weight of the twin allowed for a heavy CIWS -which appeared to have produced a destroyer with better all round firepower and AA capability than their USN treaty limited counterparts - and I believe that I have proved my case.
In the Med one standard tactic (there were others) against dive bombers was to turn under them to try and make them go past the vertical.Destroyers are quite maneuverable and SOP was turn ASAP to present the maximum amount of firepower to attacking aircraft.
Yes, and the inner layer is the most important of all, and is far more likely to score hits against DBs than HA medium calibre guns. The RN recognized this and developed the quad pom-pom to fill that need.Do you not understand that you need layered defence. Did the example of HMS Tiger whose 6in were deadly against aircraft but still needed 3in and Seact missiles not show this. That the USN with the 40mm and the 5in had the best combination going.
And at the end the 4.7 stops firing and is useless against divebombers whatever you say this is the final fact.
The first changes made were the replacement of the 0.5 with 20mm guns initially 4 then normally increased to 8 with twin mounts replacng singles. The TT were removed for the 4in, then replaced. Later the TT's were removed again and replaced with the 40mm.
On Tribals the 0.5 were replaced with 20mm, then the twin 4in replaced a twin 4.7, then as we have seen 6 x 40mm were added. You cannot make any assumptions about weight unless you know the mounting.
Where on earth did you get the RN saying the 40mm had the same effectve range of 1,700 yards.
The "Maximum Effective Ranges" of close range weapons are as follows:-
2-pdr. multiple Pom-Pom and Bofors in local control 1,700 yards.
Oerlikon 20 mm. single gun 1,000 yards.
0.5 in. Machine gun. 800 yards.
0.303 in. and 0.30 in. weapons 400 yards.
The Gunnery Pocket Book - Part 4 (para 470)
I admit I don't get this statement can you explain
I have no idea but would assume they had a basic system similar to the US DE's
Well you have failed to convince anyone.
Unfortunately that left them stuck unable to fire anything at a bomber bout to drop its load.Yes, and the inner layer is the most important of all, and is far more likely to score hits against DBs than HA medium calibre guns. The RN recognized this and developed the quad pom-pom to fill that need.
No you are wrong. No changes were made for the addition of 20mm guns and the Tribals were later able take the 40mm without any reductions in weapons. Unless you can support your statement that when the 40mm were added someting was removed from the tribals to compensate.The simple fact is that topweight compensation was required to fit increased CIWS and the post war Mk VI director.
Good find, but can I ask if you knew the effective range under local non directed control was 1,700 ish yards, why were you claiming 10,000ft?From the RN:
Good question and I don't know the reason. A guess is that pre war they decided like the UK and USN that fixed one piece shell was unsuitable for a destroyer. By the time 1944 came around they were not in a position to be so fussy.IJN fleet destroyers used a twin mount that required fixed angle loading above 10 degrees. They could have used the 5"/40 twin mount as on the Matsu's which had loading trays for all angle loading.
good infoThe US DEs had no centralized FC until late ~43/44 when the Mk 51 director (similar to the RN Simple Tachymetric Director) was adapted to give some measure of close range AA firecontrol but this was pretty useless against longer range air and surface targets. Most USN DEs used the 3in/50, BTW.
Destroyers are quite maneuverable and SOP was turn ASAP to present the maximum amount of firepower to attacking aircraft.
You keep forgetting about the pom-pom.Unfortunately that left them stuck unable to fire anything at a bomber bout to drop its load.
The 4in twin was added immediately after Norway and the 20mm came after that, and then came the 40mm Bofors - it is pretty easy to see how the topweight progressed.No you are wrong. No changes were made for the addition of 20mm guns and the Tribals were later able take the 40mm without any reductions in weapons. Unless you can support your statement that when the 40mm were added someting was removed from the tribals to compensate.
Good find, but can I ask if you knew the effective range under local non directed control was 1,700 ish yards, why were you claiming 10,000ft?
ENEMY TACTICS AND EQUIPMENT
German
German air attacks against our surface forces were more effective than those of the Japanese, prior to the latter's use of suicide tactics, for the following reasons:
German aircraft were superior.
German pilots possessed greater skill.
German attacks were more highly co ordinated.
Our own air defense was weaker.
Our surface forces were not as modern or heavily armed as those in the Pacific.
HyperWar: Antiaircraft Action Summary--World War II
You mean the pom pom, the weapon wth an effective range of approx 5,100 ft, the pom pom you claim can fire effectively up to 10,000 ft? The pom pom that the RN said was only half as effective as the 40mm against targets apart from suicide aircraft. The pom pom that even the chart you produced showing the arc of fire of an RN destroyer gave a range of approx 7,000ft, that pom pom.You keep forgetting about the pom-pom.
So we agree that the Tribals had the 4in and the 20mm before they received the 40mm guns. Which brings us back to the question you keep avoiding. Of course the toweight increased, the question is, was this a problem for the Tribal class destroyers.The 4in twin was added immediately after Norway and the 20mm came after that, and then came the 40mm Bofors - it is pretty easy to see how the topweight progressed.
There you go again, getting wrapped up in the theory, not the what happened. In Vietnam in theory the F4 didn't need a gun as the Sparrow and Sidewinder were so effective, in the real world they paid a high price for that theory. In WW2 the RN had a theory that their destroyers didn't need a HA gun, in the real world they also paid a price for that theory. In WW2 in theory Enigma was unbreakable, but the germans paid a very high price for that theory. On HMS Tiger in theory we didn't need the Seacat as we had the 3in, in the real world for various reasons we needed the Seacat, at least that was a lesson learnt in peacetime. Do I need to go on, if you wish we could cover the introduction of the M16, the SA80, the decision taken in 1938 that the RN didn't need a single seat fighter, that the Seafire didn't need additional fuel tanks, the list is endless.effective range is synonymous with a reasonable probability of getting hits (IE a well trained crew should hit within that range). It doesn't mean that hits are not possible beyond that range and your average Stuka pilot knew that a single pom-pom hit was likely to ruin his day. Also I provided a quote from March showing that the RN thought it theoretically accurate to 10,000ft.
Maybe this had something to do with itTHE USN's opinion on the Luftwaffe versus the IJNAF:
It seems very likely that these are the maximum cyclic rates possible under static (ideal) conditions and normally the gun would use the ammunition hoists (use of the hoists was mandatory during predicted AA fire) and so with handpicked guns the max RoF is 15 rpm.2) The guns installed on HMS Delhi had originally been destined for USS Edison (DD-439). These guns had been hand-picked by Edison's first commanding officer, Lt. Cmdr. Albert C. Murdaugh, who had just previously been assigned to the Naval Gun Factory at Washington, D.C. Much to Lt. Cmdr. Murdaugh's distress, President Roosevelt ordered these guns diverted to Delhi and as a result Edison did not receive her replacement guns until after she had been commissioned and had completed her preliminary trials. Perhaps as a result of having these hand-picked weapons, the gunnery officer on Delhi reported that during gunnery trials in February and March 1942 that these guns were able to fire 25 rounds per minute with the ready-use ammunition stored in the handling rooms and 15 rounds per minute with the normal supply from the magazines.
We have info from USS Maury:A total of 362 rounds were fired, 74 at the shore battery, 20 in the first engagement, and 268 in the second destroyer engagement, of which it is estimated that 200 rounds were fired at the first destroyer and 68 at the second. All firing was director-controlled, rapid, continuous fire. The average gun range for the first firing was 9,500 yards, for the second 14,000 yards, and for the third 12,500 yards... ...It is particulary pleasing that the guns maintained a sustained rapid fire of 268 rounds (average 68 rounds per gun) at an estimated rate of at least 12 shots per gun per minute without casualty.[1]
[1] United States Navy, AntiAircraft Action Summary, July 1942 to Dec 1942 (Information Bulletin No. 22), p.161-163
So 15RPM was the maximum and 12 RPM the actual RoF. Maury also report that two of her 4 guns became unserviceable after this action due to excessive bore enlargement.The sharp tang of Smokeless Powder filled the air as succeeding Salvoes roared out at five-second intervals...
The ammunition passers, mostly the new volunteers from the states, were trying so hard to keep the gun firing at its maximum rate that some of them started "saving time" by handing the projectiles directly to the shellman instead of tilting them into the fuzesetters. They had maintained a great rate of fire, but the fuzes weren't set!
http://destroyerhistory.org/goldplater/ussmaury/index.asp?r=40130&pid=40133
We know that the handworked RN 4.7in single could fire at a cyclic rate of 17.6 rpm for at least 5 rounds.
No we don't.
you are confusing burst fire with cycle rate.
The 5in/38s (and darn few other destroyer main guns) not being stabilized.
The Tribals, JKN and L-M class destroyers had DP 4.7in guns with on-mount AA fuze setters, that were controlled with the FKC HA FC system. It is true that elevation was limited to 40 or 50 degs, but they were not SP guns, as per the 5"/38 guns on the USN Porter and Somer class, which had no capability for predicted fire against aircraft. The overall AA power of a Tribal or JKLMN class was probably better than the early USN destroyers with 4 or 5 x 5"/38 DP guns, because the RN destroyers had a CIWS of a quad pom-pom and 2 quad .5in mounts versus only 4 x.5in mgs on the USN destroyers.
As for 40 degs not being enough, well that's not true; it all depends on the altitude of the attacking aircraft, obviously against a torpedo bomber or a low altitude level bomber, 40degs is plently, and against dive bombers attacking other ships, the same gun could place a barrage over the ship being attacked. If you read the accounts of the IJNAF attacks on the USN carrier task forces in 1942, you will see that the destroyers could have performed as AA escorts even with 40deg elevation. The key factor is that the guns be controlled in AA mode by a computer that can predict the movement of the target and direct the gun to the correct elevation and deflection while also providing fuze timing, and every RN destroyer from the Tribal class onward could do this. Here's the firecontrol schematic of the Tribal class (this also shows type 285 radar which was being fitted to RN destroyers from mid 1941):
Attachment 224237
The big problem for RN destroyers and 40 deg elevation guns, came when they had to operate alone or where they became the target of attacking aircraft, and then really only when they faced dive bombers. High altitude level bombing was not very effective against ships anyways, and the RN would have preferred to add an extra quad pom-pom when the dive bombing threat was realized in 1940, but these simply didn't exist so they added (spare) 3in and 4in single HA mount guns on some destroyers to allow for engaging high altitude and divebombers and a twin 4in in lieu of the after upper 4.7in mount on the Tribal class..
You don't know that the gun was loaded prior to the first round being fired - in fact why would it be, since the gun was undergoing firing trials?
I agree that any destroyer on its own was in grave danger from air attack.
The RN lost many destroyers that were acting on their own or in loose cooperation with other ships, usually withdrawing troops without air cover.
They were attacked by very professional bomber crews who had a lot of experience and were well motivated.
I do not think that USN destroyers in the same position would have fared any better.
And you don't know the gun was unloaded at the start.
Your quote "During gunnery trials in 1930, HMS Basilisk'' was able to fire "...five rounds in 17 seconds."
If it started loaded that is a cycle of rate of about 4 seconds or 15 round per minute which is quite good. it is also believable considering later performance. A cycle rate of 3.4 seconds or 17.6 rpm is just a bit too good considering the later performance.
The HMS Basilisk also used the 30 degree elevation mount. We also do not know the conditions of the trials. Speed and sea conditions affected the destroyer or type, speed (if any) of the target. Was the destroyer in calm water doing 12-15kts firing at a stationary/moored target at close ( under 3000yds) range that required little or no change in elevation and only minor changes in train? Where was the gun in relation to the ammunition hoist/feed or for 5 rounds was that even a consideration?
The L&Ms with the big 4.7s suffered a drop in rate of fire with the turrets rotated 90 degrees from the center line because the ammunition hoists did not turn with turret calling for a longer, more confused pathway for the ammunition numbers to follow.
With the Ls part of the 1937 Naval estimates ( budget?) and Ms part of the 1939 it can be seen that at least some in the RN were not satisfied with the twin 4.7 as used in the Tribal and J&K classes. The Mark XX twin hada few problems of it's own and shows the problem of trying to combine both good surface gunfire with a DP mount. The Americans sacrificed some surface capability ( muzzle velocity/range) for the DP capability.
You can find "burst fire" ratings for a number of land artillery pieces. Vickers offered a SP 155 gun that could fire 2 rounds in 8 seconds, 3 rounds in 13 seconds or an "intense" rate of 6 rounds per minute. Sustained of 2 rounds per minute for one hour. The last two firing rates may have more to do with barrel cooling and barrel life than the loading arrangements. The last certainly does. There is no way a gun using 100lb shells and bagged charges "cycles" at 4 seconds.
I did not make up "burst fire", it exists and can be found. It is perhaps more useful for advertising or press releases than evaluating combat performance.
The US 5in/38 guns were not stabilized. Heavy seas is subject to interpretation and heavy seas slow the rates of fire by throwing the loading numbers (crew) around slowing the work at the guns. Even before WW I most knowledgeable gunnery officers figured that the rate of fire "in combat" for medium sized guns on cruisers would be 1/2 to 1/3 what was achieved during the summer annual "shoots". Destroyer guns using lighter ammunition ( and cased charges rather than bagged) would show less of a fall off until the weather got really bad.