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BB main gun accuracy

Discussion in 'Ships & Shipborne Weaponry' started by harolds, Nov 18, 2011.

  1. harolds

    harolds Member

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    Has there been any comparisons on the accuracy of WWII era BBs main guns? For instance, what was dispersion of shells at some given range? Or, at what range could these BBs keep all, or even half, of their shots into the area of another BB? This question is on the inherent accuracy of the guns and not on their fire direction computers. I would think that the various navies had done testing on these weapons before they were adopted. Is this data still available, if so could someone summarize it? Thanks in advance.
     
  2. belasar

    belasar Court Jester Staff Member

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    I recall reading in Hitler's Italian Allies that the Italian navy had real problems with accuracy as due to poor quality contol on ammunition and powder production.
     
  3. USMCPrice

    USMCPrice Idiot at Large

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    Takao and Carronade are probably the best two members here to answer your question. Their knowledge on things naval never ceases to amaze me. Guys, what's the answer?
     
  4. 1ST Chutes

    1ST Chutes Member

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    In a large way this question is loaded in that the FCS and other systems such as radar are largely responsible for the accuracy of the battery in relation to the target. The inherent accuracy of a gun relies on the data of the FCS for range, elevation, atmospheric conditions , charge etc. The data gained by eithier Call for fire, pre-plot or radar or even optical ranging by the vessel is crucial in determining the accuracy of the fire mission.


    For instance in the 80's an Iowa class with each turret equipped with a DR810 FCR could place 15 rounds in 0.64% in a 220 yard sheaf relative to the target with a 123 yard shell to shell dispersion. Take away advanced FCR and and advanced FCS and you can probably add 75 to 150 yards in total sheaf dispersion firing dumb on a whizz wheel and darts and charts.


    Another question would be are talking about an area bombardment target, a point target or a point ship to ship target?
     
  5. harolds

    harolds Member

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    Actually, the FDC and it's equiptment tells the guns where to shoot, not how well the guns will shoot. However, I'm looking for the inherent accuracy of those naval rifles. In other words, If you fire X number of rounds at Y range, all with the exact same deflection and elevation, and from the exact same position, all other factors the same, how close together will those rounds land. This has implications for both ship2ship and shore bombardment.
     
  6. Carronade

    Carronade Ace Patron  

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  7. 1ST Chutes

    1ST Chutes Member

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    I'm aware of what FDC does for an Artillery Battery I'm also aware of what CIC does on a Naval Vessel. Perhaps I convoluted something in my translation, so let me try again.

    In the 8 years I spent as a Naval Gunfire Spotter I never saw a vessel fire cold with no firing solution from CIC / Gunnery so I am going to assume at some point the firing guns were given a firing solution.

    I have however observed USN DD's, FF's,CGN's FFG'S & USCG Cutters conduct ship direct missions on shore targets. To keep this relative I'll only note what I observed and/or what the instruction and SOP was for 5"38 guns and 16'50 Mk 7 guns.

    What I observed was that rounds from all Naval guns fall in a vertical or near vertical sheaf in orientation to the designated target as is common for NGFS , (this also why Danger Close on NGFS is a greater range than Arty when the GTL passes over friendlies). 5"38 on a fire for effect (FFE) tended to stay with in a 100 to 150 meter sheaf in a FFE.

    General instruction for a adjustment round on a good coordinate was +/- 500, depending on method of location.

    On a FFE on a fully adjusted mission was +/- 30 from the designated target.

    On an I/S or SEAD the instruction was +/- 100 meters

    So if the salvo is 5 rounds contained in a 150 meter sheaf your looking at a dispersion within sheaf of about 30 meters per round, give or take.

    16" 50

    The sheaf characteristics as far as fall of sheaf remain in a roughly vertical orientation.

    From a good coordinate the first round is +/- 500 meters depending on method of location.

    FFE from final adjustment is +/- 100 to 50 meters.

    The two BB missions I saw fired with Missouri's Main Battery and the one Crater analysis I conducted were a sheaf with a roughly a 100 to 125 meter round dispersion within sheaf.

    Keep in mind all these missions were fired in the 80's and 90's with guns that were far better equipped with radar and FSC support and firing solutions.

    As far as inherent accuracy I would surmise that if the above missions were fired without benefit of a dedicated FCS or CIC then you could probably go +/- 50 with the 5" 38, +/- 250 with the 16" 50.

    I have never seen a table that takes in 16"50, 16"45, 18" etc as far as round dispersion or any publication from either the USMC or USN that compares any of them nor reports outside of individual vessel and TF AAR's.
     
  8. TiredOldSoldier

    TiredOldSoldier Ace

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    Pretty intertesting, read a recent article on Italian gunnery that attemped to prove it was not that different from other nations, the final hit counts on medium and long range engagements in the Mediterranean seem to fit pretty well with that theory, on the other hand the bad QA on Italian charges is a historical fact, some ship gunnery oficers were known to compensate for that (simply re-weighting all charges and organizing them into homogenuous groups), but even then it did add one additional element to the fire control calculations.
    On curious info in that article was that at Samar the average Japanese spread was considered too small, (200 to 300 yards) greatly reducing the changes of achieving a hit, there is a quote of the captain of USS Hoel on spreads of 50 yards at 8000m so actually the guns were too accurate and the spead failed to compensate for the fire control errors (of course if you achive a straddle with a close spread the results can be devastatingf (ex: HMS Hood).

    Below the errors for some Italian guns he reports from live trials at full charge (so under ideal conditions)
    381/50 (OTO manufacture) at 21.000m horizontal spread 290m range spread 267m
    381/50 (Ansaldo manufacture) at 22.500m horizontal spread 416m range spread 364m
    For the 320/44 OTO I only have second charge data
    320/44 (OTO manufacture) at 16.400m horizontal spread 400m range spread 547m (1940 tests)
    320/44 (OTO manufacture) at 15.100m horizontal spread 145m range spread 216m (1941 tests)
    320/44(Ansaldo manufacture) at 23.600m horizontal spread 620m range spread 159m
    Cruiser guns -------------------
    203/53 Ansaldo at 18.200m horizontal spread 197m range spread 262m (1939 tests)
    203/50 Ansaldo at 18.900m horizontal spread 197m range spread 289m (1939 tests)
    152/55 at 15.800m horizontal spread 278m range spread 405m (1939 tests)
    152/53 Ansaldo at 16.800m horizontal spread 168m range spread 226m (1939 tests)
    152/53 OTOat 15.900m horizontal spread 194m range spread 253m (1939 tests)

    Annoying thing is he doesn't provide any info on how many rounds were fired on on wheter it was single or salvo fire (could be significant for the single craddle gun mounts of the cruisers).

    BTW I think the sort of dispersal you can get on a shore bombardment mission is better than what you can get in a gun duel, the ship is moving steady, not attemping to avoid return fire and there is less pressure on the crew.
     
  9. lwd

    lwd Ace

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  10. harolds

    harolds Member

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    Ok everyone, we have an answer for the Iowa Class BBs. They could put their shells in pattern or group that was 1.9% of the range in WWII. This was bettered considerably in later years. We also had some data on Italian guns though it was in a different format. I haven't gone over that one carefully, but obviously the quality in the manufacture of the guns and ammunition were the biggest factor in a gun's inherent accuracy. Does anyone have any data on German, Japanese or British BB guns? If that data does surface, it will probably be in different formats since each nation had a different way of evaluating accuracy. If we can get the data I will try to summarize it here for anybody who is interested.
     
  11. lwd

    lwd Ace

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    I believe I've read that 3% of range was considered good for pre WWII battleships. There is some info from training shoots by both the US and the RN. The KM as well I believe. I think I've seen numbers on one or more of the battleship boards.
     

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