Range of Bismarck's guns

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paul.mercer
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Re: Range of Bismarck's guns

Post by paul.mercer »

Hi Bill,
Just a thought, but in a straight 'stern chase' surely the ship running away (assuming that it had two aft turrets (or one four gun as on PoW) that ship would have just as much chance to land some damaging hits on the pursuing ship even possibly more so as the bridge and fire control would be at the front? In other words, stern chasing is a rather hazardous undertaking.
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RF
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Re: Range of Bismarck's guns

Post by RF »

paul.mercer wrote: Wed Nov 17, 2021 10:28 am Hi Bill,
Just a thought, but in a straight 'stern chase' surely the ship running away (assuming that it had two aft turrets (or one four gun as on PoW) that ship would have just as much chance to land some damaging hits on the pursuing ship even possibly more so as the bridge and fire control would be at the front? In other words, stern chasing is a rather hazardous undertaking.
I am no gunnery expert but would not the lead ship in firing directly astern have a disadvantage in that the speed/velocity of the shell would be reduced by the forward motion of the ship, whereas the chaser would fire shells whose velocity would be faster by the speed of pursuit?
''Give me a Ping and one Ping only'' - Sean Connery.
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Re: Range of Bismarck's guns

Post by Bill Jurens »

You are correct, but the range difference is usually of practical insignificance, as one can easily adjust for ship motion effects by simply adjusting the angle of departure. At extreme ranges, when the angle of departure (at least in theory) approaches 45 degrees, it might be possible for this to make a difference, but at those ranges the time of flight is so long -- and the effects of trunnion tilt so large -- that one is largely dependent upon pure luck to hit anyhow.

The effects of ship motion, which tend to increase range when guns are fired over the bow, are to a large extent mitigated by the fact that when firing over the bow one is also firing into a motion-created wind.

So, overall, I would not think that ship motion would be of much interest except in quite unusual cases. In practical terms, the problem is -- or was -- solved by 'spotting', i.e. the total effects on range were corrected by simply increasing or decreasing angle of departure a bit with little consideration as to exactly why such an effect might be required. In a situation where the target and firing ship are in nearly constant relative positions "Down 200" solves all of this more-or-less automatically. Also works if firing ship and target are in nearly constant relative motion, e.g. if the target ship is steaming away on a more-or-less radial vector and the firing ship is stationary. In such cases the so-called 'range rate' becomes nearly constant and predictable, and range to target at any particular moment is easily computed with quick reference to a stopwatch.

Bill Jurens.
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