I introduced the mountain howitzer class and traced some of the history in an earlier post. Today I will detail the standard mountain howitzer used during the Civil War.
As mentioned before, the Model 1835′s design borrowed heavily from a French weapon of this class. But the U.S. Army intended to use its mountain howitzers on terrain ranging from swamps to high mountains. The Model 1835 followed a simple form. A recess over the chamber, base ring and muzzle ring interrupted the otherwise plain tube form. A standard knob topped the flattened conical breech face.
The Mountain Howitzer’s chamber measured 2.75 inches in depth and 3.34-inches in diameter, technically about “4-pdr” gauge. Through the length of a 2.75 inch neck, the cylindrical chamber expanded to the full 4.62 inch bore diameter. These dimensions, smaller than the standard 12-pdr Field Howitzer which had a 4.25 inch deep chamber with a 3.67 inch diameter, meant the mountain howitzer used less powder than its contemporaries firing the same caliber projectiles.
Differing from the French design, the Americans opted for larger, centered trunnions. However, at 2.7 inches in diameter, the mountain howitzer could not use standard field carriages. The chart below compares the field howitzer types to the mountain howitzer particulars on the fight hand column.
Mentioned in the previous post on mountain howitzers, artillerists had three options for moving the Model 1835. The basic carriage weighed 515 pounds configured for towing by one horse or mule. A separate pack animal carried ammunition.
As displayed in the figure, the saddle designed for the mountain howitzer featured a transom with notches in line with the trunnions. This allowed the artillerists to break down the carriage and weapon for pack onto two animals (again with a third carrying the ammunition).
Some secondary accounts claim gunners could fire the howitzer off the back of the horse in this configuration. I would simply ask the logical question in response – to what tactical good?
By the 1850s, the Army found a need to move the mountain howitzer at a gallop or behind two horses for higher speed on the open plains of the west. The resultant arrangement became the prairie carriage and resembled a miniature field carriage in many respects. The configuration weighed 940 pounds with limber.
Each mountain howitzer ammunition chest contained two shells, five case, and one canister. The Model 1835 used the same shell and spherical case projectiles as a standard 12-pdr field howitzer. But due to the smaller chamber, it used half the powder charge. The howitzer used fixed ammunition, with the powder charge fixed to a sabot formed to fill the neck of the chamber. A strap then bound the case or shell to the sabot.
However, the mountain howitzer’s canister round differed from the standard 12-pdr canister. While the field issue canister used 1.05-inch diameter cast iron balls in the “can,” the mountain howitzer used 0.69-inch lead musket balls. By regulation 4 layers of 37 musket balls gave the 12-pdr mountain howitzer canister 148 balls.
Being a smoothbore muzzle-loader, some of the mountain howitzer drill matched that of the field pieces. But the piece required enough special instructions for handling that the Army issued a set of supplemental instructions in 1851. In terms of tactical considerations, again the small size of the mountain howitzer factored into planning. For example instructions noted the Model 1835 when deployed as a section in battery fronted 10 yards with a 31 yard depth. But a field howitzer in the same configuration fronted 18 to 21 yards with a 47 yard depth. Smaller cannon means smaller footprint.
Generally, smaller cannon also equated to shorter range. Every reference including those from the Civil War period state the maximum range of the 12-pdr mountain howitzer was 1005 yards, firing a shell with 0.5 pounds of powder, at 5 degrees of elevation.
Personally I raise a question here with regard to that performance. Frankly, it does not square with what I know of ballistics. For starters, the listed range of the 12-pdr field howitzer, firing the same projectile at the same elevation, but with a full pound of powder is 1072 yards. So adding half a pound of powder improves performance by only 67 yards?
Furthermore, the stated rage graduations from the instructions indicate some jump in performance as the elevation was increased. Consider this comparison between the regulation range tables for the 12-pdr Model 1841 Field Howitzer and the Model 1835 Mountain Howitzer:
In spite of the initial gap in performance below 2 degrees, projectiles fired from the mountain howitzer seemed to close the gap with the field piece as elevation increased. So I have to ask, if both pieces were elevated to 6 or 7 degrees, would the little mountain howitzer out range its larger field counterpart?
A standard rule of ballistics reasons that, all things being equal, the weapon with the longer bore offers better range. The Model 1835 had a bore length of 5.5 calibers compared to 9.36 calibers for the Model 1841 Field Howitzer. Perhaps even more telling, the Navy’s 12-pdr heavy boat howitzer, with a slightly longer bore at 10.8 calibers, ranged to 1085 yards (firing a 10 pound shell, with a one pound charge, at five degrees elevation).
On the other hand, maybe the Army’s Artillerist Manual, as cited in the previous article, provides a clue to the Mountain Howitzer’s remarkable range table. Recall that John Gibbon wrote, “The total range of the mountain howitzer sometimes reaches 1200 yards, after the shell has ricocheted three or four times.” Perhaps the range indicated for the mountain howitzer included one or two of those ricochets?
So are all those manuals wrong? Is the cited range for the mountain howitzer in error? Or was it done knowingly to conceal the limitations of the weapon system?
One thing I am sure of though, the 12-pdr Model 1835 Mountain Howitzer played an important role in American history, not just military history. While serving with some distinction during the Civil War, it was out west that the little mountain howitzer found the most use.
Aside from on site notes and links provided above, sources consulted for this post were:
Hazlett, James C., Edwin Olmstead, and M. Hume Parks. Field Artillery Weapons of the Civil War, Revised Edition. Urbana and Chicago: University of Illinois Press, 2004.
Ripley, Warren. Artillery and Ammunition of the Civil War, 4th Edition. Charleston, S.C.: The Battery Press, 1984.
French, William, William Barry, and Henry J. Hunt. Instruction for Field Artillery. US War Department. New York: D. Van Nostrand, 1864. Reprinted by Stackpole Books, 2005.