Comparison: US and Foreign 6-pdr Guns

Those of us with Cold War experience may fondly recall the old ASCC reporting names for aircraft and missiles.  For those who were not gifted with such experiences, in short the NATO countries, along with allied nations around the world, standardized an artificial set of names for Soviet hardware.  Those artificial names served as a framework when discussing the perceived capabilities of the aircraft or missiles.  But not knowing with precision exactly what the Soviets called their weapons lead to a lot of misidentification and incorrect perceptions.  For the historian dealing with such things, we have to work from a perspective of “what did they know at that time?”… furthermore we must ensure that knowledge, or lack thereof, is used as the context when interpreting the sources.

In the 19th century, armies “looked over the shoulder” of their potential adversaries – and allies – just the same as today.  While perhaps not cloaked an air of “James Bond” and all, there was indeed some technical intelligence gathering going on.  With respect to field artillery, we find that manifested in a section within the US Army’s Ordnance Manuals with a title something like “Cannon of Foreign Countries.”

From the 1841 edition:

The materials for the following table have been collected, with few exceptions, from the latest manuals of artillery in England, France, Prussia, and Austria, and from memoranda obtained in Russia and Sweden.

The dimensions and weights are given in our own measures.

The column of exterior length shows the length from the rear of the base ring to the face of the piece, and the length of bore includes the chamber, when not otherwise mentioned.

In England, France, and Sweden, howitzers and mortars take their denominations, as with us, from the diameter of the bore, or from the caliber of a gun of corresponding bore; in Austria and Prussia, from the weight of a stone ball of the caliber of the bore; in Russia, from the true weight of the shell.

This introduction identifies the sources used, to which I would add some data was undoubtedly derived from examination of cannon – particular those captured from the British during the Revolution or War of 1812.  And that point is one good reason to have data on the cannon of other countries – should the situation arise that American officers need to use captured or otherwise acquired weapons.

The introduction also lets us know the data was converted to American standards.  Though at the same time we see just settling on “the name of a thing” was as difficult then as it is today.

In the past, I’ve used the tables to compare foreign and American 24-pdr howitzers.  There we were focused more on weapons imported during the Civil War.  If we switch over to the 6-pdrs, there were certainly some imports to consider.  But also we might use those tables to compare US weapon development to that of Europe.  Much of the American’s research, development, and test programs focused on the 6-pdr caliber between 1815 and 1855.  And some of the data, which made its way onto those Ordnance Manual tables, was used to assess American work.  That in mind, let us consider the data:

6pdrForeignComp

Please note the color coding here.  Green lines are field guns (many, even heavy types, specifically labeled field gun in the tables).  Rose colored lines are siege, garrison, seacoast, or naval guns.  And that one yellow line is for a mountain gun, included simply because the caliber rating in the manual. Entries from England, France (only the earliest manuals), Spain, Belgium, Austria, Prussia, Saxony, Russia, and Sweden.  To that I added listings for US models from 1919 up to the Civil War.  And for good measure, the experimental Griffen wrought iron gun.

As alluded to in the manual’s introduction, the table included bore diameter, exterior length (minus the knob), bore length, and weight.  There were also columns that rated the windage allowed.  While that was an important factor with field artillery, a lot of variables played in there. Worth discussion at a later time perhaps.

The columns for focus in our discussion today are those detailing the length and weight.  And to narrow that focus more, I’ve added a column to show the ratio between the length of bore (in inches) to the weight of the gun (in pounds).  In other words, how much metal was allocated against the length of travel down the bore?

Why that?  Well, length of bore factors into the interior ballistics of the weapon.  And interior ballistics in turn begets exterior ballistic performance.  Guns have longer bores than howitzers, of course.  But beyond that, when comparing a gun of shorter bore to one with longer bore, there are performance differences to keep in mind. And there are limitations that govern the practical length of the bore.  One of those is the weight of the weapon.  In a simple equation, one would desire the longest bore possible within a given weight.  But… we are reminded the thinner the metal, the more susceptible the gun to bursting or other metal performance problems.  All this said… and again, running the risk of over simplification for sake of brevity… the optimum 6-pdr gun would be one with the longest bore, yet with just enough metal thickness (around the breech, mostly) to ensure good performance and reliability.  But not one pound of metal more!  (lest we start discussing the ratio of horse power to pound of gun…)

But not all metals are the same, you say!  Correct.  In the scope of mid-19th century conversations, there was cast iron and bronze (steel, wrought iron, and other options, we’ve discussed before… were more novelties at that time).  Furthermore, prior to the 1840s, copper, the necessary base for bronze, was mined in only small quantities (Vermont was the leading producer, BTW).  But the early United States had plenty of iron!  Later, after the big Michigan copper rush, the War Department realized the US was gifted with plenty of both metals.

All that background in mind, what do we see with the ratio of bore length to weight?  Well, the Model 1819 “Walking Stick” cannon, of cast iron, had a lower ratio than many European bronze weapons.  In fact, it was almost as low, in ratio, to the British light bronze 6-pdr (which the Americans were very familiar with).   A longer bore, and with a much denser metal, yet the Americans left it relatively thin around the breech.  Only 75 pounds heavier and with about five inches more bore.  Would have been interesting to see range trials between those weapons.

On the other end of the time line, the last mass produced American 6-pdr, the Model 1841, was much heavier, by ratio, than the Model 1819 iron gun.  Nearly four pounds per inch of bore heavier!  This made the Model 1841 heavier, again by ratio, than the Napoleonoic era British and French guns.  (And that is a fine point that I lack space to fully develop here – the French and British move to 12-pdr guns as the century progressed.. topic for another day.)  Yet, the Model 1841 does not stand out as overly heavy compared to the other European powers. Particularly when considering the Belgian guns.

The thumb I’d put on the scales here is with respect to the model numbers.  We have documented efforts by the Americans to develop an acceptable (Secretary of War Joel R. Poinsett might say “perfect” in the sense of perfection being the enemy of good in this case) field gun.  Acceptable in 1819 was a cast iron gun of relatively light weight.  By 1841, even a bronze gun needed more mass of metal – more than a third more, by ratio of bore to overall weight.

Why?  One word – gunpowder.  Despite having few wars during that first half of the Pax Britannica period, the technology of warfare did not sit still.  By 1861, there was nearly a half century of innovation and refinement to apply towards the grim task of warfighting.

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