George Elder wrote:... supect this might be the case? With regard to intelligence as it relates to shell weights and initial MVs, these data were published in Brassey's and other journals, and most of the data is fairly reliable. Indeed, even in the 1920s they were putting in cross-sectional diagrams of some shells, etc., IIRC. But this focus on drag vs cross-sectional area and weight only tells part of the story. The flight characteristics of the shell itself can generate a good deal of added resisitance via its influence on the relative cross-sectional area of the shell. As you know, even spin-stabilized shells wobble a bit depending on their mass distribution relative to their length, width, and form. This yaw, although small, can effect drag and V losses -- or so I am advised. My understanding is that the Germans did a lot of wind-tunnel research in this area, and it would not overly surpise me if they found a way of maximizing flight "balence" in ways that mitigated losses in V over distance. Here we particularly think of flight effects in the last half of the range. I have seldome seen this issue addressed, and find myself wondering if your current set of formulae take the wobble/yaw effect into consideration. I shall forward this to Dr. Don C, who teaches ballistics, if it is deemed of importance. He doesn't have a heck of a lot of time, but this very interesting -- at least to me. Yes, you have got me very curious about all this. Some interesting notions and possibilities here.
This is sort of what I am driving at although I wasn’t thinking specifically along the lines of this sort of physical causation -- i.e. in-flight wobble etc. The British had already developed a correction factor for determining a projectiles ballistic coefficient for in-flight stability well before World War I. The so-called "coefficient of steadiness". So the concept was understood and adjustments were made to a projectiles BC accordingly.
But you can’t separate pesky diameters and weights and mathematics from an understanding of exterior ballistics. No one after all could physically measure in-flight velocity during this period when a projectile was 10,000-yards down range and a mile up in the air – well maybe Baron Von Munchausen could. But Joe Firing Table Maker Guy would have access to some empirical information from range testing – chronograph data, yaw card data etc etc . But this may be limited to range determined information which covers only several hundred yards from the muzzle. You may also have resistance\retardation firing data for a specific projectile over a number of velocities – adjusting initial charge accordingly. A ballistician of the period would than have to extrapolate this into a full blown set of range tables using common drag functions that might extend out to 25,000 or 30,000-yrds or more. A well written set of firing tables of this period will generally detail what was assumed for a drag function, what was assumed for a form factor, and what was assumed for a projectiles ballistic coefficient -- or some combination thereof. Of course modern military proving grounds don’t use common drag functions to develop FTs anymore. But they did in WWI and WWII.
Sadly, in a large percentage of cases, official range tables remain classified, inaccurate, or frankly non-existent.