Long Range Gunnery

[Bgile]

An old British battleship (HMS warspite) hit an Italian battleship at a range of about 26,000 yds in 1940. That tied for the longest range hit in WWII. No battleship had the opportunity to fire at another battleship at a range much greater than that.

Why do people use this fact to argue that it's pointless to attempt to hit another ship at any range greater than that five years later in 1945? Were there not major advances in technology between 1940 and 1945? Why is it so hard to believe this is possible?

[Mostlyharmless]

Why do people use this fact to argue that it's pointless to attempt to hit another ship at any range greater than that five years later in 1945?

We are all too lazy to carefully analyze Iowa and New Jersey's action with Nowaki, which should represent the state of the art for February 1944. We know that the range was 35,000 yards to 39,000 yards and that Nowaki was not hit. However, I do not know how many shells were fired, how many salvos straddled Nowaki or what was the dispersion of the salvos. I also do not know what course was steered by Nowaki but I assume small changes to get away as quickly as possible while making the American gunnery difficult. I gather that some problems arose from the calculation of barrel wear leading to frequent 'overs'.

There might also be examples where guns around the Straits of Dover fired at enemy ships at long range to analyze from 1942-4. As these targets would have been slower than Nowaki and the guns would not have to correct for their own motion, this would give a more optimistic estimate.

[Bgile]

I wonder if that information is available somewhere. I honestly wouldn't know where to look. Muir wrote about it in his book on US battleships, so I assume he had access to it somewhere and culled it. I suppose it's possible he just interviewed someone. I don't believe he lists his source, which is a shame.

[RF]

There might also be examples where guns around the Straits of Dover fired at enemy ships at long range to analyze from 1942-4. As these targets would have been slower than Nowaki and the guns would not have to correct for their own motion, this would give a more optimistic estimate.

Are land based guns really comparable to those mounted on a ship, with the ships roll and motion etc?

[Bgile]

Are land based guns really comparable to those mounted on a ship, with the ships roll and motion etc?

Because of those factors, I'd think land based guns should be more accurate. They also benefited from very long base rangefinders.

[lwd]

...WII. No battleship had the opportunity to fire at another battleship at a range much greater than that....

I believe POW fired at and may have straddled Bismarck at around 30,000 yards.

...
We are all too lazy to carefully analyze Iowa and New Jersey's action with Nowaki, which should represent the state of the art for February 1944.

Not so. It's been analyzed to considerable detail and discussed often on this board.

We know that the range was 35,000 yards to 39,000 yards and that Nowaki was not hit. However, I do not know how many shells were fired, how many salvos straddled Nowaki or what was the dispersion of the salvos.

A Japanese document posted some time ago over on the IJN board indicated that Nowaki did take some splinter damage. I've seen acounts of the salvos and most were stradles even though many were only 3 gun salvoes.
http://www.combinedfleet.com/katori_t.htm
credits the opening salvos of both BBs with stradles.

http://books.google.com/books?id=rrRaqV ... ey&f=false
Indicates Iowa fired 40 rounds in 5 salvos and New Jersey 18 rounds in 7 salvos claiming a hit on the 4th salvo which may be a good bet for the source of the splinter damage.

And from:
http://acgmag.com/forums/showthread.php?t=12400&page=10

Much credit must be given to IJN Nowaki's skipper,CommanderSetsuji Moriya. Commander Dale of USS Bunker Hill was spotting fall of shot over IJN Nowaki & opined that "this was a real smart [destroyer] captain. As soon as he saw the belch of the 16 inchers, he changed course about 45 degrees & held it until the shells splashed, which were then well off in deflection, then he resumed his base course."

It is also worth remembering that Iowa and NJ were traveling at over 32 knots and maneuvering as well.

[Byron Angel]

It has been a while since I looked into the NOWAKI engagement, but the two salient points I recall are (a) the engagement was a classic stern chase, (b) the engagement involved very long ranges of 35,000+ yards.

At such distances ToF (at least 50 to 60 seconds) was a major consideration and provided NOWAKI ample opportunity to evade in deflection. Even a modest 15 deg change of course made in reaction to the observed discharge of a broadside would have laterally displaced NOWAKI a couple of hundred yards by the time the salvo landed without really sacrificing any speed. Under such conditions, hitting would have been practically impossible for the American BB's in pursuit.

[Bgile]

It has been a while since I looked into the NOWAKI engagement, but the two salient points I recall are (a) the engagement was a classic stern chase, (b) the engagement involved very long ranges of 35,000+ yards.

At such distances ToF (at least 50 to 60 seconds) was a major consideration and provided NOWAKI ample opportunity to evade in deflection. Even a modest 15 deg change of course made in reaction to the observed discharge of a broadside would have laterally displaced NOWAKI a couple of hundred yards by the time the salvo landed without really sacrificing any speed. Under such conditions, hitting would have been practically impossible for the American BB's in pursuit.

Well, since shells would be hitting anywhere within what ... 300 yds or so ... of MPI and 16" HE has a fairly large lethal radius, and frag damage to hull or stacks could cause slowing ... not impossible. Also, maneuvering causes some loss in speed, even with only 15 deg change of course. How fast was Nowaki? Remember, ONE hit close enough to slow the ship and it's all over for her.

Obviously that didn't happen, but the people on Iowa and New jersey obviously thought it wasn't "practically impossible" or the attempt would not have been made, right?

[Byron Angel]

Well, since shells would be hitting anywhere within what ... 300 yds or so ... of MPI and 16" HE has a fairly large lethal radius, and frag damage to hull or stacks could cause slowing ... not impossible. Also, maneuvering causes some loss in speed, even with only 15 deg change of course. How fast was Nowaki? Remember, ONE hit close enough to slow the ship and it's all over for her.

Obviously that didn't happen, but the people on Iowa and New jersey obviously thought it wasn't "practically impossible" or the attempt would not have been made, right?

..... I looked into Navweaps and found that the ToF of a HC 16-in round at the ranges in question was actually about 70 to 80 seconds, so the FC solution for HC seems rather more difficult than I anticipated. The Navweaps site also cites USN data which expected about 1.4 percent hits against an end-on target of BISMARCK size at 30,000 yards. Given the greater evasive maneuverability of a DD target, its much smaller target area (about 1/4th), the greater range, and the poorer ballistics of 16-in HC rounds, I'd estimate that the likelihood of hitting cannot have been expected to be better than about one-quarter of one percent, which = about 250 rounds expended to achieve a 50/50 chance of at least one hit. Strictly my opinion of course.

Also, in such a long-range stern chase, the critical issue would have been deflection and the critical salvo dimension would have been width. My estimate is that the width of a 16-in pattern at such ranges would have been on the order of 100-150 yards (Bil Jurens or Tiornu or Brad Fischer might have specific data on this). My estimate is that, with NOWAKI evading in deflection against a 70-70 second ToF, the nearest shells would have been landing 150 to 200 yards distant.

The fact that both US BB's did fire upon NOWAKI is clear evidence that the respective gunnery officers did not view the gunnery situation as futile, but it is I think fair to say that it represented a pretty darned difficult case for them.

[tommy303]

Bureau of Ordnance predicted pattern size for the 16in to be about 1% of the gun range when using the 2700-lbs shell. I am not sure about how the HC faired.

[Bgile]

I have successfully downloaded Tom's pdf file, and it was a very interesting read. The following quote is taken from "The Evolution of Fleet Tactical
Doctrine in the U.S. Navy, 1922–1941 by Trent Hone:

"The Navy’s gunnery exercises provided further support for the idea
that the concentrated fire of a battleship division could rapidly inflict
crippling losses. During an exercise in fiscal year 1935, the battle line
achieved 60 hits for 1,179 shots on a target raft at a mean range of
27,450 yards. Had the target been battleship-sized, there would have
been roughly 3.33 hits per minute per ship. With about 20 hits necessary
to sink a battleship, the concentrated fire of a three-ship division could
destroy an enemy battleship in approximately two minutes."

The entire article reinforces the fact that the USN planned to fight at the maximum range possible, using aircraft spotting. At that time, the maximum range was 33,000 yards for the Colorado Class and 35,000 yds for the New Mexico and California classes. The others would have been spectators at any range over 23,000 yds and 21,000 yds for some, due to the 20 deg elevation restriction.

I know the jury is still out for some here and it always will be, and there are definitely other things to consider. I'm looking forward to doing some more reading on this topic.

[dunmunro]

I have successfully downloaded Tom's pdf file, and it was a very interesting read. The following quote is taken from "The Evolution of Fleet Tactical
Doctrine in the U.S. Navy, 1922–1941 by Trent Hone:

What pdf file are you referring to?

[Brad Fischer]

Why do people use this fact to argue that it's pointless to attempt to hit another ship at any range greater than that five years later in 1945?

We are all too lazy to carefully analyze Iowa and New Jersey's action with Nowaki, which should represent the state of the art for February 1944. We know that the range was 35,000 yards to 39,000 yards and that Nowaki was not hit. However, I do not know how many shells were fired, how many salvos straddled Nowaki or what was the dispersion of the salvos. I also do not know what course was steered by Nowaki but I assume small changes to get away as quickly as possible while making the American gunnery difficult. I gather that some problems arose from the calculation of barrel wear leading to frequent 'overs'.

Unfortunately, many of the second source accounts of the skirmish off Truk have left out details or even, sadly, inflated the truth a bit. New Jersey opened fire at 32,200yds followed three minutes later by Iowa at a range of 35,700yds. Contrary to what has been written only Iowa straddled on her first salvo with New Jersey “scoring” her first straddle on the 4th salvo and another possible one on her 6th. Iowa is the one who straddled on the first salvo but didn’t after that as Nowaki altered course to port 25* and Iowa subsequently lost both optical and radar track and no observation or tracking was possible for the last two salvos.

New Jersey’s problems weren’t with incorrect wear assessment, although there were problems with the differential modifiers for the 16-inch Mk 6 & 7 range tables, but rather her problems mostly stemmed from not having warm guns and firing two and three gun salvos from alternating turrets. The cold gun phenomenon is quite vexing and can have a one sigma IV delta of as much as +/- 25 f.s. Very vexing and they didn’t even overcome it even in the 1980s when they understood the cold gun phenomenon the best (much more than in the 1940s.)

Once the guns were warm the IV became very stable, demonstrating as little as +/- 5 f/s with little or no “hot gun rundown” as the barrels continued to heat up over a prolonged period. In the 1940s they believed the guns were warmed after one round but they found, through extensive testing in the 1980s that it really took 3 rounds (per gun) for them to be up to warm and stable operating temperature. So in reality New Jersey’s guns never got up to temperature since she fired 18 rounds out of 6 guns. Iowa didn’t suffer this same problem since she had already fired 8 salvos at Katori.

New Jersey’s other “sin” was firing “partial salvos” from alternating turrets. This is less of a problem that the cold gun problem but it can lead to problems since each turret, much like each gun in a turret, exhibits differing ballistics. This is a problem in partial salvo firing because if the spot coordinator doesn’t bias the spot for the next group to fire, he will be inadvertently applying for the next salvo based partially on characteristics of another set of guns. Another issue with partial or split salvo firing is that 3-gun salvos are less stable and exhibit a larger salvo-to-salvo shift of the MPI. The spot coordinator must be cognizant of this phenomenon so he won’t apply to much spot corrections from salvo to salvo trying to “chase the spot”; this was known as “ping-ponging” the spot.

Brad Fischer

[Brad Fischer]

It has been a while since I looked into the NOWAKI engagement, but the two salient points I recall are (a) the engagement was a classic stern chase, (b) the engagement involved very long ranges of 35,000+ yards.

At such distances ToF (at least 50 to 60 seconds) was a major consideration and provided NOWAKI ample opportunity to evade in deflection. Even a modest 15 deg change of course made in reaction to the observed discharge of a broadside would have laterally displaced NOWAKI a couple of hundred yards by the time the salvo landed without really sacrificing any speed. Under such conditions, hitting would have been practically impossible for the American BB's in pursuit.

Hi Byron,

You’re exactly right, Nowaki was “running for the hills” and BatDiv 7 was shooting at her in a stern chase. To make matters worse, the two BBs had to alter course to unmask the forward group which made for a diverging course which meant high range rates. Not really a problem per se, but it did mean reduced time to score a hit before the target escaped as happened historically.

It’s interesting that you mentioned maneuvering out of a deflection pattern. A while ago Tony Lovell wrote a java based real time simulation of the US main battery fire control system where the program operator could track a target just like the Mark 8 rangekeeper operator would. It included a Mark 8 radar scope for spotting so that the program would simulate blind fire conditions. It was incomplete but you tracked a target exactly as a real rangekeeper would and its results were quite comparable to the results observed in both exercise and combat.

What I found was not really surprising but interesting nonetheless. End on fire is, as you suggest, a very difficult problem. I found attempting to hit a maneuvering BB target (never mind a DD sized) end on difficult at long ranges. Many times I made runs where I thought I was popping the target consistently only to find out that I never straddled in deflection (a constantly maneuvering target). I even made a run simulating this engagement and found that it was difficult to score hits consistently in the short time allotted for the engagement.

Of course there are some substantial variations between my sim and the conditions present during the actual event. One is that by the time the BB’s opened fire Nowaki was already hulled down and as noted in Iowa’s action report, only the top of Nowaki’s superstructure and masts were visible from Spot I. This meant that it was difficult to discern target angle from optical means which is substantially faster than it would be by rate control tracking. Hence the turns wouldn’t be observed until rate control tracking detected them via range/bearing observations. Nowaki made two turns, one of 20 degrees and the other of 25 degrees before both ships lost all tracking data. This would easily put her well outside 9-gun deflection pattern.

Brad Fischer

[Brad Fischer]

Also, in such a long-range stern chase, the critical issue would have been deflection and the critical salvo dimension would have been width. My estimate is that the width of a 16-in pattern at such ranges would have been on the order of 100-150 yards (Bil Jurens or Tiornu or Brad Fischer might have specific data on this). My estimate is that, with NOWAKI evading in deflection against a 70-70 second ToF, the nearest shells would have been landing 150 to 200 yards distant.

Pretty good estimate. BuOrd listed the deflection TMD as +/- 0.051% of range. A 3-gun salvo would be expected to produce a deflection pattern of 0.124% of range while a 9-gun pattern would be 0.2% of range; at 35,000yds that’s 45 and 70yds. Those are not representative of deflection patterns on ship as you have mounting and training errors in there as well. Generally the average deflection pattern was 2-4 mils; i.e. 70-140yds at 35,000yds.

The fact that both US BB's did fire upon NOWAKI is clear evidence that the respective gunnery officers did not view the gunnery situation as futile, but it is I think fair to say that it represented a pretty darned difficult case for them.

Very true as this was clearly promulgated in ComBatPac’s GUNNERY DOCTRINE which called for, among things, the opening of fire during a daylight engagement at a range no later than 32,000yds (“…if no signal is received all ships are expected to open fire by 32,000yds.”) and to close to maximum radar spotting range. So it’s clear that the USN at least felt that long range gunnery was a viable tactic but I also agree with your premise that the engagement off Truk was a very difficult gunnery problem.

Brad Fischer