Famous Monitor's XI-inch Dahlgren Shell Guns

Saphroneth · Oct 27, 2022

trice said:
Put yourself in the late 1850s. Dahlgren is one of the world's greatest authorities on gunnery (some would say the best of them). Dahlgren does not know what is going on. He believes that at some point muzzle velocity becomes too high. He thinks that it then begins to degrade accuracy and has some results that lend credence to that idea. Dahlgren has enough data to know something is happening that he cannot explain exactly, but he does not know what it is.

Is there somewhere that Dahlgren talks about this? It might be interesting to see at what point he considers the effect to come in - for example the 11" at 15 lbs powder when firing shell (not shot) has an initial velocity of 339 yards per second, per Buckner, which is mach 0.9 and well into the regime where a round cannonball of that diameter has sharply rising drag.

ED: The 9" when firing with 10 lbs (with shell) also has an initial velocity of mach 0.9.

Belfoured · Oct 27, 2022

Saphroneth said:
As noted, Buckner's table from 1865 explicitly uses an interpolation formula based on drag and values found by experiment. All that is necessary to give a starting point is values found by experiment, and you can interpolate between the two values after that.

There's error-compounding calculations you can do to work out how uncertain each individual value found by experiment would be, depending on the gun's deviation at given ranges.

Fair enough but by "at the time of the Civil War" I meant shortly before/during. Buckner's tables were approved in early 1865, and as "sufficiently" - but not "theoretically" - accurate. If you're aware of earlier such tables, I'd welcome that. I don't have Benton's treatise in front of me but as stated my recollection of the 1859 edition is that the discussion of ballistics was limited.

67th Tigers · Oct 27, 2022

trice said:
How would the gunner get such a table?

Put yourself in the late 1850s. Dahlgren is one of the world's greatest authorities on gunnery (some would say the best of them). Dahlgren does not know what is going on. He believes that at some point muzzle velocity becomes too high. He thinks that it then begins to degrade accuracy and has some results that lend credence to that idea. Dahlgren has enough data to know something is happening that he cannot explain exactly, but he does not know what it is.

I'd like to read Dahlgren discussing this because (1) it is incorrect, and (2) it had been understood about 100 years at this point that pushing the MV to 1,500 or 1,700 fps increased the accuracy of fire. Most naval ordnance was in the 1,600 fps velocity region. Shell guns fired at a lower velocity, and much experimentation had been done with them.

trice · Oct 27, 2022

Saphroneth said:
Is there somewhere that Dahlgren talks about this? It might be interesting to see at what point he considers the effect to come in - for example the 11" at 15 lbs powder when firing shell (not shot) has an initial velocity of 339 yards per second, per Buckner, which is mach 0.9 and well into the regime where a round cannonball of that diameter has sharply rising drag.

ED: The 9" when firing with 10 lbs (with shell) also has an initial velocity of mach 0.9.

Dahlgren's works are available to read. It is some time since I read from them. From memory, his point as written was about muzzle-velocity in general across any gun; not about a specific gun or a specific powder charge. In his ordnance work from 1847 on, he tested many guns of many different sizes in addition to designing his own in various sizes.

From the Memoirs, apparently taken from something he submitted in 1850:

Saphroneth · Oct 27, 2022

Belfoured said:
Fair enough but by "at the time of the Civil War" I meant shortly before/during. Buckner's tables were approved in early 1865, and as "sufficiently" - but not "theoretically" - accurate. If you're aware of earlier such tables, I'd welcome that. I don't have Benton's treatise in front of me but as stated my recollection of the 1859 edition is that the discussion of ballistics was limited.

Well, rather my point is that we know (from this example) that calculated range tables were done by starting from empirical data and then interpolating with some formula or other, rather than by doing raw calculations. Buckner happens to be the source I had available which was official and which explained the methodology it used.

In Dahlgren's Shells and Shell-Guns book, part II, he explains how the ranges of various guns were found. It was, not to my especial surprise, from empirical data.
He starts off by talking about how he had to set up triangulation so the splash could be located, as he was firing into the water, rather than firing along the shore (owing to the specific situation in the river he was working in and so on). He notes two cases of ten rounds being fired, where the two range-estimation stations set up agreed on the average value to within 0.4 yards.

When he gives range tables, he specifies how many rounds make up the data for each elevation.

Saphroneth · Oct 27, 2022

trice said:
Dahlgren's works are available to read. It is some time since I read from them. From memory, his point as written was about muzzle-velocity in general across any gun; not about a specific gun or a specific powder charge. In his ordnance work from 1847 on, he tested many guns of many different sizes in addition to designing his own in various sizes.

From the Memoirs, apparently taken from something he submitted in 1850:

View attachment 456100

Having searched on this phrase, I find it mentioned in the 1870 court case around his death.

I will point out here that the (VI) summary of the letter states that there is a fixed relation between the mass of a shot or shell and its velocity which is essential to accuracy of flight was Dahlgren's position.

This seems to suggest (to my reading at least) that in the 1849 letter he's not actually talking about a specific and invariant "everything goes wrong" velocity which is constant across gun calibres. Instead the velocity varies with the mass of the ball.

In his 1851 report he does indeed state that there's a velocity that you can't exceed (and that you should increase the mass, not the velocity) but without more information it's actually quite hard to tell what velocity he's talking about. Given the focus in his work on bouncing the cannonballs across the water, I wondered briefly if it could be related to skipping the ball across the water, but he prescribes shell (not shot) on the next page:

And he talks about the precise velocity that would give the greatest practicable accuracy.

I have to admit, I'm at a loss as to the effect Dahlgren could be talking about here - if you're willing to put in the rounds to establish range for a given muzzle velocity (and he was, he fired one experimental gun over 1,000 times until it burst) then everything about the behaviour of a smoothbore should be completely predictable except for the last-bounce and corresponding Magnus effect, plus the wind.

In Shells and Shell-Guns, Dahlgren states (as a rule) that "Accuracy is derivable from the uniformity of axial motion, inevitably incidental to all military projectiles of whatever shape, and the configuration of the trajectory". In the following section he talks about how the Lancaster gun, because of having a smaller muzzle velocity than a smoothbore of similar diameter (because it's heavier and has a smaller charge) would have to be fired at a higher trajectory *and that would make it less accurate*.

He also says that "(so far as) the relative accuracy of the two projectiles depends on the directness of the trajectory, the round ball will have the advantage at the lower elevations, the elongated at the higher". So a flatter trajectory for the same range is an advantage.

He repeatedly specifies in Shells and Shell-Guns that a flatter trajectory is an advantage.

If we could locate the report from September/October 1849 we'd be able to actually tell what he's talking about. I can't find any mention of the effect in Shells and Shell-Guns itself, so it's at least possible that it was a theory he'd dropped by the time he wrote the book - that or he didn't feel it worth putting it in, though it contains just about everything else.

Total aside, but in the checking on what Dahlgren said in Shells and Shell-guns about accuracy I think he commits the sharpshooter fallacy. He says at one point that ten shot passed through a four foot square area of a screen at which the gun was aimed, at 260 yards, but that at 1300 yards only three shot out of ten struck a screen 40 by 20 yards, and says this shows the hit rate was much less despite 50 times the area. It's not clear whether he realized that effectively he got to cherry-pick the bit of the screen the gun was aimed at after the fact for the 260 yard firing but not for the 1300 yard one.

trice · Oct 27, 2022

Saphroneth said:
Having searched on this phrase, I find it mentioned in the 1870 court case around his death.

View attachment 456102

I will point out here that the (VI) summary of the letter states that there is a fixed relation between the mass of a shot or shell and its velocity which is essential to accuracy of flight was Dahlgren's position.

This seems to suggest (to my reading at least) that in the 1849 letter he's not actually talking about a specific and invariant "everything goes wrong" velocity which is constant across gun calibres. Instead the velocity varies with the mass of the ball.

In his 1851 report he does indeed state that there's a velocity that you can't exceed (and that you should increase the mass, not the velocity) but without more information it's actually quite hard to tell what velocity he's talking about. Given the focus in his work on bouncing the cannonballs across the water, I wondered briefly if it could be related to skipping the ball across the water, but he prescribes shell (not shot) on the next page:

View attachment 456103

And he talks about the precise velocity that would give the greatest practicable accuracy.

I have to admit, I'm at a loss as to the effect Dahlgren could be talking about here - if you're willing to put in the rounds to establish range for a given muzzle velocity (and he was, he fired one experimental gun over 1,000 times until it burst) then everything about the behaviour of a smoothbore should be completely predictable except for the last-bounce and corresponding Magnus effect, plus the wind.

In Shells and Shell-Guns, Dahlgren states (as a rule) that "Accuracy is derivable from the uniformity of axial motion, inevitably incidental to all military projectiles of whatever shape, and the configuration of the trajectory". In the following section he talks about how the Lancaster gun, because of having a smaller muzzle velocity than a smoothbore of similar diameter (because it's heavier and has a smaller charge) would have to be fired at a higher trajectory *and that would make it less accurate*.

He also says that "(so far as) the relative accuracy of the two projectiles depends on the directness of the trajectory, the round ball will have the advantage at the lower elevations, the elongated at the higher". So a flatter trajectory for the same range is an advantage.

He repeatedly specifies in Shells and Shell-Guns that a flatter trajectory is an advantage.

If we could locate the report from September/October 1849 we'd be able to actually tell what he's talking about. I can't find any mention of the effect in Shells and Shell-Guns itself, so it's at least possible that it was a theory he'd dropped by the time he wrote the book - that or he didn't feel it worth putting it in, though it contains just about everything else.

Total aside, but in the checking on what Dahlgren said in Shells and Shell-guns about accuracy I think he commits the sharpshooter fallacy. He says at one point that ten shot passed through a four foot square area of a screen at which the gun was aimed, at 260 yards, but that at 1300 yards only three shot out of ten struck a screen 40 by 20 yards, and says this shows the hit rate was much less despite 50 times the area. It's not clear whether he realized that effectively he got to cherry-pick the bit of the screen the gun was aimed at after the fact for the 260 yard firing but not for the 1300 yard one.

Please do not try so hard to dismiss things you cannot fit into your POV.

Dahlgren is talking about the actual problems he is seeing in testing guns. From his work, he deducts that something happens at some point where high velocity begins to cause inaccuracy. In his 1849 and 1850 writing, he is talking about a hypothesis to explain an observed problem.

As we know, there actually is a difference in the ballistics when the muzzle velocity exceeds the speed of sound. If you want to speculate on why he is saying there is a difference, it is because there actually is one.

Beyond that, none of the tools he would need to determine what was actually going on exist in 1850. The very concept of a "sound barrier" does not exist (certainly not widely known or discussed) for about another 80 years or so. While Ernst Mach was actually alive in 1850, I do not think his work on shock waves came until well-after the Civil War -- he and his son used photography to examine them, so maybe the 1880s or 1890s.

If you want to criticize Dahlgren, explain how he is to discover what you want without any tools and no known theory to explain what is going on. Recall that he has no computers to do math or visualization or run simulations. No way to observe and collect the necessary data on the phenomenon.

The first actual picture of an airplane breaking through the "sound barrier" is this one of an FA-18 Hornet from 1999.

18_Hornet_breaking_sound_barrier_%287_July_1999%29.jpg

I wonder what Dahlgren would have said if someone explained that picture to him. Picture a cannonball replacing the plane in it.

ADDED LATER:
The actual first photo of the bow wave of a supersonic object by Ernst Mach, 1887:

y_of_bow_shock_waves_around_a_brass_bullet%2C_1888.jpg

Saphroneth · Oct 27, 2022

trice said:
Please do not try so hard to dismiss things you cannot fit into your POV.

That's not what I'm doing. I'm trying to determine what effect it is he actually found (in terms of the physical ramifications and actual physical effect), and also why he didn't put it into his shell-guns book when he did repeatedly mention that higher trajectories were worse for accuracy. (You'd think he'd have mentioned it there, if anywhere.)

It's related to how accuracy and range tables actually work. If I may.

There are, fundamentally, three ways to get the individual range entries you get on a range table. These are effectively essential for using a cannon in the field, simply because you can't rely on either point-blank range (i.e. elevation does not matter) or working it out by hand every time from first principles, or by doing undershot-overshot starting from no data.

The first way is empirical. This means that for a given powder charge and elevation, you fire the gun off a number of times and record where it lands each time. You then average the results, and you have your range-elevation value.

The second way is that you work it out from a formula. This formula must take into account, at minimum, the effects of gravity and drag for it to be correct enough to use; it doesn't have to be precise, though, it can simply be an approximation.
It's not really possible to come up with a formula entirely from first principles without ever firing the cannon, so what you'd do is start from some known range-elevation values and fit an equation to those known points, then use it for the rest of your points.
(This can mean for example that you work out a formula at one velocity and then apply it to a higher velocity.)

The third way is through interpolation between already known points. This just means you assume that the range-elevation curve in that section is flat, or slightly curved (if you want to use a slightly more fancy formula) and, well, mathematically interpolate. The simplest example of interpolation is that you take halfway between two points and take the arithmetic mean of the elevation and range values, but there are others.
The benefit of this is that it reduces significantly the number of ranging shots you need to do.

Now, the reason why I outline that is that - unless there is a physical effect I am missing - the effect of the variable drag at high mach numbers is consistent. It's not easy to predict by formula, but it produces consistent empirical effects.
This means that the main way I can see it causing Dahlgren to see lower accuracy is if higher muzzle velocity shots go "off formula" relative to lower muzzle velocity shots. That is, he uses some formula* to estimate the range at X degrees at 1,400 fps muzzle velocity, and then when he tests it the range results he gets are not correct. (That is, his formula has turned out to be incorrect for

This is an entirely plausible sequence of events that could cause Dahlgren to conclude that higher muzzle velocity is inaccurate. He has a formula, and it predicts the correct ranges for the elevation at low muzzle velocities but not at high ones.

However, this is not the same as Dahlgren's conclusion being correct (that high velocity shots are fundamentally inaccurate). This is because - again, unless there is a physical effect I am missing that only applies at high velocities - a range table generated based off empirical results at high muzzle velocities should produce correct range estimates.
If you fire ten times at 2 degrees at 1,400 fps, and that gives you the range (1,000 m), the eleventh round should land roughly there.

* for example, a formula which effectively assumes the drag coefficient is constant - which is exactly what Buckner did in 1864-5. He has a different but constant drag coefficient effectively determined based on empirical data and curve fitting for each combination of projectile and muzzle velocity, which manifests as a given % of the velocity of the projectile being shed each 1/4 of a second.

It is quite possible that there is some physical effect, or the ramifications of it, that I am missing and that leads to high velocity shots producing inaccurate shots even with an empirical range table. Absent this, however, high velocity shots aren't intrinsically inaccurate - they're just off formula.

trice · Oct 27, 2022

Saphroneth said:
Absent this, however, high velocity shots aren't intrinsically inaccurate - they're just off formula.

You need to examine what you are saying and revise it.

If they are "off formula" then they are inaccurate. If your formula does not accurately describe the ballistic performance of the projectile, then your formula is inaccurate (IOW, wrong).

Saphroneth · Oct 27, 2022

trice said:
If they are "off formula" then they are inaccurate. If your formula does not accurately describe the ballistic performance of the projectile, then your formula is inaccurate (IOW, wrong).

Yes, that's what I'm saying. I'm saying that (in my hypothesis), Dahlgren had a formula which did not work at high initial velocities, but which did work at low initial velocities.

Saphroneth · Oct 27, 2022

The 1855 treatise on naval gunnery by General Sir Howard Douglas, Bart. (4th edition, revised) begins the discussion of accuracy by saying that the basic parabolic theory only works at very low muzzle velocities (a few hundred feet per second).

He explicitly states that "long and powerful solid shot guns" have greater range, accuracy and penetrating force in distant firing.

He explicitly states that accuracy is gained as elevation is reduced, and as greater muzzle velocity is produced.

He states that a smooth and perfectly spherical ball could be fired as accurately as a rifle.

He states that long guns are more accurate at moderate ranges, and that the greatest accuracy is achieved with the largest charge (to allow the least elevation), and that reduced charges should not be used unless the action takes place "within point-blank range or at close quarters".

He mentions that a gun of insufficient mass could be induced to shake about when fired and that this could impair the accuracy. I make special note of this because it's a possible cause of Dahlgren's inaccuracy worries at high powder charges.

The 32 pounder at 10 lbs charge has an initial velocity (given in a table) of 1600 feet per second. It is specifically stated to have been significantly more accurate in tests at 1250 yards range than the 8" shell gun with 10 lbs of powder (though this still had an initial velocity of 1418 feet per second). At 1000 yards range the 32 pounder's velocity has dropped to 803 feet per second (also in a table) and so it's clear that the 32 pounder projectile has gone through the whole transsonic transition; the irregularity in this case (if it exists) from greater velocity is overwhelmed by the inaccuracy from a hollow projectile.

It is explicitly stated that greater velocity equals greater accuracy, both because of a lower trajectory and also because of the greater velocity itself.

I also want to quote the following:

70. In contemplating the nature of the resistance to the flight of shot or shells it must be remarked that , in the motion of a body through the air , no particle of that fluid can be disturbed without moving others to a con siderable distance about it , while the displaced particles take time to fall back into the space which they before occupied . As the moving body passes on , there is left behind it a kind of vacuum more or less complete ac cording to the degree of the body's velocity ; and when the ball moves quicker than the air can rush into the space left behind , the vacuum becomes perfect . Now there is a certain limit to the velocity with which air can rush into a vacuum , viz . , about 1300 or 1400 feet in a second , and , consequently , when the velocity of a ball is greater than this , it is manifest that the resistance will be very great ; for there being then no pressure ofthe fluid behind the ball , while that which is in its front is in a state of condensation from the particles there not being able immediately to escape , the ball will be re sisted by the whole pressure of the condensed air on its fore part.

71. The resistance, besides depending on the velocity, diameter, and the weight of the projectile, is affected by so many circumstances which cannot be duly estimated, that experiment alone can determine it, and this only to a certain extent. If shot could be discharged so accurately as to hit a ballistic pendulum at considerable distances, the loss of velocity occasioned by resistance might be easily found ; but such a degree of accuracy cannot be obtained, and the ballistic experiments have hitherto only furnished us with these results at different distances as far as 300 feet, beyond which shot cannot be directed with sufficient accuracy to hit the block.

The bolded section has been bolded because it is, in fact, a pretty fair statement of the effect of the speed of sound on the resistance to a projectile. This to my mind conclusively proves that all the points mentioned above about greater velocity being beneficial were not made in ignorance of the concept of the sound barrier (insofar as it could affect the trajectory of a ball) but in a pretty good cognizance not merely of the effect but of the cause thereof.

trice · Oct 27, 2022

Saphroneth said:
Yes, that's what I'm saying. I'm saying that (in my hypothesis), Dahlgren had a formula which did not work at high initial velocities, but which did work at low initial velocities.

First, that is what I have been telling you for months. The ballistic formula for a projectile fired above the speed of sound is not the same as the one for a projectile fired below the speed of sound. Dahlgren is clearly saying that there is something about higher velocity that makes the shot inaccurate in his 1849 report and the 1850 letter. He knew nothing about the "sound barrier", but he knew there was an unexplained problem before him.

Second, the task Dahlgren is working on when he wrote that September 1849 report is the test firing of the USN 1845 standard ordnance: all six types of 32 pounders and the new 8 inch shell guns. His results led him to conclude that the heavier 32-lbers lacked accuracy while the lighter 32-lbers lacked power. He is proposing the development of a new gun to simplify all this, a heavier gun that can fire shell and shot (which would also simplify a logistical mess).

As part of his testing, Dahlgren is plotting the fall of shot and the trajectories to the best of his ability. He is not trying to match the shots to a pre-existing formula, AFAIK -- but he would certainly be trying to make sense of inconsistent results. He is working from the data, not trying to make the data match a theoretical construct.

In November 1849, Dahlgren was almost killed when a 32-lber being tested had a breech explosion. A little after that, he got permission to design his proposed new gun (the IX inch). His design was submitted in January 1850. His design was based on the concept in the 1849 report, mentioned in the 1850 letter.

Your approach to all this seems to me to block you from the real situation.

Saphroneth · Oct 27, 2022

trice said:
First, that is what I have been telling you for months. The ballistic formula for a projectile fired above the speed of sound is not the same as the one for a projectile fired below the speed of sound.

That is not what I was trying to say.

I was trying to say that Dahlgren (in my hypothesis, which is a hypothesis and not confirmed) had a formula into which the inputs were "muzzle velocity" and "elevation" and for which the output was "range", and which worked except at high velocities.

What I've been trying to understand, or trying to get you to explain, is this.

If we start with an empirical set of values forming a range table for a muzzle velocity of 1,400 feet per second, or higher, then in what way would the firing of a cannon at 1,400 feet per second deviate from that table?

If it doesn't, then doesn't that mean that the gun is actually accurate?

You yourself said that the definition of inaccuracy was:

trice said:
My use of the word "inaccuracy" is this: the shot will be less likely to hit where the gunner believes it will.

But if the gunner has a range table for a cannon at 1,400 feet per second, the gunner has all the information he needs to believe correctly where the projectile will land, right?

The only ways I can reconcile what I know about the physics with Dahlgren's statements consist of the following.

1) There is some physical effect which means that a high velocity projectile deviates from an empirical range table, in a way that a low velocity projectile does not. In this case the high velocity projectile would indeed be inaccurate because no range table could capture its behaviour, but I do not know what that physical effect could be.
In this case, Dahlgren would be correct, but I do not see what the physical mechanism could be. It is not the higher drag coefficient because that is predictable and consistent between firings.

2) Dahlgren's statements in his late 1840s and early 1850s letters refer to his tests not matching up with the range table he has determined (in some way, possibly through calculation) and he has concluded (at the time, though perhaps not by the time he wrote Shells and Shell-Guns) that this is the projectile being inaccurate.
In this case, Dahlgren would be observing the effects of the higher drag coeffiicent. He would, however, not be correct in claiming that it was impossible for a high velocity projectile to be accurate, because all that is required is a better range table.

Now, in the 1855 treatise which I read and quoted from extensively, this inaccuracy-at-high-velocity effect does not get mentioned and instead the principle that higher accuracy is obtained from higher velocity is reiterated over and over. The treatise does mention that the resistance of the air to the projectile increases markedly at high velocities, in a specific way.

This tends to reinforce my sense that (2) is the correct situation, though I am of course open to what the physical effect could be that causes (1).

To make sure that I am not misunderstood:

The physical effect I am looking for is not the higher drag coefficient at higher velocities, because that effect is consistent between different firings and can be used to construct an empiricial range table. I am looking for an effect that would cause a higher velocity projectile to behave differently than an empirical range table.

trice · Oct 28, 2022

Saphroneth said:
...
To make sure that I am not misunderstood:

The physical effect I am looking for is not the higher drag coefficient at higher velocities, because that effect is consistent between different firings and can be used to construct an empiricial range table. I am looking for an effect that would cause a higher velocity projectile to behave differently than an empirical range table.

Once again, you know and have known for a long time that there actually is a specific effect that causes a higher muzzle velocity projectile to behave differently than a lower muzzle velocity projectile. Why are you looking for something you have been shown multiple times already?????????

Saphroneth · Oct 28, 2022

trice said:
Once again, you know and have known for a long time that there actually is a specific effect that causes a higher muzzle velocity projectile to behave differently than a lower muzzle velocity projectile. Why are you looking for something you have been shown multiple times already?????????

I'm going to try and put it a different way.

If you fire a cannon at 1400 fps muzzle velocity at 2 degrees elevation ten times, and average out where the projectiles land, that gives you an empirical range for that cannon at 1400 fps muzzle velocity at 2 degrees (e.g. 1000 metres), correct?

If so, and you fired the cannon at 1400 fps muzzle velocity at 2 degrees elevation, expecting it to land at that range, would your expectation be borne out or not?

For a cannon to be accurate, it is not necessary that the projectile behaves the same at higher velocities as it does at lower velocities. It is only necessary that it behaves the same in multiple firings at the same settings.

trice · Oct 28, 2022

Saphroneth said:
I'm going to try and put it a different way.

If you fire a cannon at 1400 fps muzzle velocity at 2 degrees elevation ten times, and average out where the projectiles land, that gives you an empirical range for that cannon at 1400 fps muzzle velocity at 2 degrees (e.g. 1000 metres), correct?

If so, and you fired the cannon at 1400 fps muzzle velocity at 2 degrees elevation, expecting it to land at that range, would your expectation be borne out or not?

For a cannon to be accurate, it is not necessary that the projectile behaves the same at higher velocities as it does at lower velocities. It is only necessary that it behaves the same in multiple firings at the same settings.

Look, your approach is failing you. You need to step back, abandon it, and look for a new one. You are trying to apply your vision to a situation you either do not understand or accept.

Dahlgren, in 1850, is dealing with real-world limitations you are ignoring. He has come across an issue and is speculating on the cause of it. He needs to have a clue about it because he is trying to design new guns -- so he absolutely cannot have the "empirical range table" for guns that do not exist yet. No gun designer could. Your attempts here assume that he could and does. Your approach will never allow you to succeed in your search.

Saphroneth · Oct 28, 2022

trice said:
Dahlgren, in 1850, is dealing with real-world limitations you are ignoring. He has come across an issue and is speculating on the cause of it. He needs to have a clue about it because he is trying to design new guns -- so he absolutely cannot have the "empirical range table" for guns that do not exist yet. No gun designer could. Your attempts here assume that he could and does. Your approach will never allow you to succeed in your search.

I'm going to ask you again.

You have a gun with a muzzle velocity of 1,400 fps (such as, just for example, an 8" shell gun with a powder load of 10 lbs of powder), and you fire it ten times at 2 degrees elevation, and you average out the ranges they reach (giving you an empirical range).

Then you fire it for an eleventh time at the same elevation.

Will it behave according to the empirical range that has been measured?

Saphroneth · Oct 28, 2022

Remember, if Dahlgren is observing this effect from practical tests, before designing his new guns, he is observing it on a gun that already exists. He has the gun in his possession. It is the gun on which he is doing the tests which show the effect he's writing about.

He takes that gun, whatever it is, and fires it ten times at maximum safe powder load at 2 degrees elevation. He notes down the range each time. There is some mean range from those observations, which forms an empirical range.

Then he fires it an eleventh time.

Does the range he gets accord with the results of the empirically derived range, or not?

trice · Oct 28, 2022

Saphroneth said:
I'm going to ask you again.

You have a gun with a muzzle velocity of 1,400 fps (such as, just for example, an 8" shell gun with a powder load of 10 lbs of powder), and you fire it ten times at 2 degrees elevation, and you average out the ranges they reach (giving you an empirical range).

Then you fire it for an eleventh time at the same elevation.

Will it behave according to the empirical range that has been measured?

Please explain why you expect anyone to have this data for a gun that does not exist yet?

Saphroneth · Oct 28, 2022

trice said:
Please explain why you expect anyone to have this data for a gun that does not exist yet?

See my previous post. The gun is whatever gun Dahlgren has where he noticed whatever this effect was.

Perhaps it was a 64 pounder, which has a muzzle velocity easily into the supersonic range, but I don't know for sure - but if Dahlgren was noticing this effect, obviously he's noticing it on a gun that actually exists and that he's testing.

Again.

He takes that gun, whatever it is, and fires it ten times at maximum safe powder load at 2 degrees elevation. He notes down the range each time. There is some mean range from those observations, which forms an empirical range.

Then he fires it an eleventh time.

Does the range he gets accord with the results of the empirically derived range, or not?

Famous Monitor's XI-inch Dahlgren Shell Guns

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