The Power of the M-1841 12-Pound Mountain Howitzer

During the summer of 2021, I had the privilege of working for the National Park Service at Fort Laramie National Historic Site (NHS) in Wyoming. At Fort Laramie, the Park Service interpretive staff demonstrated the power of the M-1841 12-Pound Mountain Howitzer.

The author next to a replica Mountain Howitzer, Fort Laramie NHS. Source: Author

Before firing a blank round from the Howitzer, the staff made the visitors “earn” it by giving a half-hour presentation on just what a M-1841 12-Pound Mountain Howitzer is. The M-1841 12-Pound Mountain Howitzer is best understood by breaking down the name.

First up, what does the “M” stand for? That’s the easiest one. In this context, “M” means military. More specifically, the United States military with the United States Army as the primary branch operating the Howitzer.

The U.S. military adopted the M-1841 12-Pound Mountain Howitzer in, you guessed it, 1841. But 1841 was only the year the military adopted the M-1841 12-Pound Mountain Howitzer for official use. Before 1841, the U.S. Army needed to test the effectiveness of the artillery piece. The Army ordered 13 units for testing in 1837. One of these was carried by John C. Frémont, the “Pathfinder,” on his Second Expedition to explore and map the Oregon Trail in 1843–1844. Frémont abandoned the howitzer in late January 1843 in a canyon on the east side of Sonora Pass, in the Sierra Nevada Mountains. In the 1990s, a few wrought iron parts of Frémont's howitzer were found. These parts are on display at the U.S. Forest Service Ranger office in Bridgeport, California.

One reason Frémont chose to take a 12-Pound Mountain Howitzer was due to the “mountain” aspect of the name. For the M-1841 12-Pound Mountain Howitzer, “mountain” essentially means “off-road,” or the same as saying “4X4” on a modern pickup truck. To transport the artillery piece off-road, it needs to be broken down. Pull two pins and the barrel of the piece is released from the carriage. The barrel weighs 220 lbs. - the barrel must weigh at least 200 lbs., or the Army would reject it as being lightweight and inferior - and can be strapped to the back of a mule. Pins also release the wheels from the main body of the carriage. The wheels and body can then be strapped to the back of a second mule. A third mule can carry the ammunition. Therefore, the M-1841 12-Pound Mountain Howitzer can go anywhere three mules can travel.

Diorama of mules carrying an 1841 Mountain Howitzer, Fort Garland Museum & Cultural Center, Colorado. Source: Author

Next up, why is it called a “12-Pounder?” Because it fires a 12-pound cannon ball I hear you say. Well, you are close. If the M-1841 12-Pound Mountain Howitzer fired whole cannon balls, then yes, it would indeed fire a cannon ball weighing 12-pounds. But the M-1841 12-Pound Mountain Howitzer was not designed to fire solid shot cannon balls. The M-1841 12-Pound Mountain Howitzer was optimized for firing explosive shells. An explosive shell is a cannon ball which is hollow and then filled with gunpowder. So, in reality, saying the howitzer is a 12-pounder really is designating the caliber. In this case, the 12-pounder is a 4.62-inch caliber or 117.35 mm caliber.

The Howitzer is of smoothbore design. This means, you guessed it, the bore is smooth inside. This is opposed to a rifled bore. Rifling means spiral grooves have been cut on the inside of the barrel. The grooves force the shell to spin when it is fired and the spin acts to stabilize the shell in flight, giving it greater accuracy. The effect is the same as a quarterback throwing a football with a tight spiral. Right now, you are probably asking, “if it leads to greater accuracy, why aren’t all barrels rifled?” Rifling leads to greater manufacturing problems and cost. Because of the added complexity and cost, the 12-pounder made due without a rifled barrel. As the saying goes, close counts in horseshoes, hand grenades, Mountain Howitzers.

The explosive shell, the 12-pounder fired, is equipped with a Bormann Time Fuze. The Bormann Fuze is “cut” or “punched” in quarter-second intervals. Using a table, the artillerymen would cut a fuse for a time to correspond to the range. Say the enemy is 800 yards away and the howitzer is set to fire at a 2-degree angle. The fuze would be cute for 2¾ seconds. When the Bormann Fuze ignites the gunpowder inside the shell, the shell explodes, and - if timed right - shell fragments will rain down on the enemy as deadly shrapnel. The Native American Indians who witness the American howitzers named them the “gun that goes boom twice.” The first boom from the cannon firing the shell. The second boom - taking place in our scenario 2¾ seconds later and 800 yards down range - was from the shell exploding overhead of the target. You may have seen movies depicting artillery fire. In some movies, great clumps of earth are kicked up by artillery fire. That cannon crew should be court-martialed for ineffectiveness, or at least the movie director should be for historic inaccuracy. The movies which get it right are the ones that show a small puff of black smoke above the battlefield showing the shells exploding overhead.

In addition to explosive shells, the howitzer could also fire spherical case and canister shot. Spherical case is similar to an explosive shell but has the addition of having 44”-caliber musket balls added into the interior of the shell along with the gunpowder. This makes the shell heavier and lowers its overall range but makes the spherical case shell a more effective anti-personnel weapon. For the ultimate in anti-personnel chargers, a cannoneer could also fire canister shot. This looks more like a coffee can than a cannonball and is loaded with 144 of the 44”-caliber musket balls. Loading a howitzer with canister shot essentially turns the piece into a giant shotgun. The downside, the canister round only has a range of about 300 yards, so if the commander calls for canister, you know the enemy is right upon you.

If the approaching enemy did indeed make it through the barrage of canister fire, the cannon crew had one last responsibility before retreating. They would “spike the gun.” Spiking the gun meant driving a nail or similar object into the fuse whole. This would prevent the cannon from being able to fire until a gunsmith could come and clear out the blockage. The crew would spike the gun because, as you were running away, the last thing you would want is the enemy loading and firing your own cannon back on you.

An original Mountain Howitzer on display in the 1876 Guard House at Fort Laramie NHS, Wyoming. Source: Wikimedia Commons

Finally, we get to the howitzer part of the name. Roughly speaking, there are three types of artillery pieces. The cannon, the mortar, and the howitzer. A cannon, sometimes also called an artillery gun, fires projectiles at a relatively flat trajectory. One use for a cannon is at sea on Navy ships. There are not a whole lot of hills at sea to get into the way of a flat long-range projectile. The mortar is essentially the opposite of the cannon. A mortar fires its shell at a high arc, think of a pop-up fly in baseball. This makes the mortar ideal for use against a fortified position. Have a castle with high walls or an enemy in a dug-in position? Then use the mortar to fire an artillery shell up and over the fortification. Now, remember who the U.S. Army was fighting in the Great Plains and West in the nineteenth century, the Native American Indians out here were mobile. They followed the buffalo and had no use for forts or walls. But, you may encounter a hill or two, even out in the Plains, so a compromise artillery piece is needed. The howitzer falls in between the cannon and the mortar. It can fire shells at relatively long rangers - not quite as long as a cannon, but longer than a mortar - and it can fire at an angle - steeper than a cannon, but not quite as high as a mortar - which means it can fire at hills. The M-1841 12-Pound Mountain Howitzer has a range of 1,005 yards (919

m) at +5° elevation with a charge of 0.5 pounds (0.2 kg) of black powder when firing shell.

The author as part of a cannon crew (position 1) at Fort Laramie NHS. Source: Author

A nineteenth century artillery crew could have as many as eight members. Most artillery regiments were stationed along coastal fortifications. The 4th artillery regiment did patrol the interior of the continent. G Battery was at the Battle of Blue Water Creek in 1855 when General William Harney engaged the Brulé Sioux Indians. Then, for a short time in 1858, Companies A and I of the 4th were stationed at Fort Laramie. But overall, most of the artillery in the Western U.S. was performed by “jackass artillery” crews. As the name implies, jackass crews were cobbled together by cavalry and infantry men. Often, they were “volen-told” that they were part of the artillery crew and forced to practice on the artillery in addition to their other duties. Because of the hodgepodge nature of the crew, often the artillery operated without its full assortment of eight cannoneers. To be remotely effective, the crew needed four men to fire the cannon and one to prepare the ammunition. The cannon crew at Fort Laramie NHS often looked like…

Position 1 - Carried the ammunition from the limber

Position 2 - Cleaned the bore and rammed the round home.

Position 3 - Inserted the Bormann Fuze into the bore and pulled the lanyard firing the cannon

Gunner - (And you thought it was going to be 4) - In charge of the piece, tended the vent, and gave the commands

Position 5 - Prepared ammunition and cut Bormann Fuzes

The Gunner would call the cannoneers to attention, and then call out the range and shell he wanted. Position 5 would prepare the shell called for and cut the Bormann Fuze for the desired range. Position 1 would walk back from the piece to the artillery limber and retrieve the shell Position 5 had prepared. Position 1 carried the shell back to the piece in a leather pouch. Why go through the trouble of placing the shell in a leather pouch just to walk it back 15 feet? In the heat of battle, there would be sparks from all of the other guns firing. Position 1 did not want the round going off in his hands, so the leather pouch protected it from stray sparks.

While Position 1 and 5 were preparing the ammunition, Position 2 was preparing the piece. He would swab the barrel with a wet rag. This would clean the barrel, and also get rid of any loose sparks or embers from the previous firing. Again, you don’t want the round to catch a spark and go off early. The Gunner would adjust the elevation of the cannon for the range he wanted. He would also tend the vent. Tending the vent involved covering the fuse whole with his finger. The Gunner wore a leather thumb guard to protect his fingers from the heat of the barrel. Why the need to tend the vent? Covering the fuse whole prevented oxygen from entering and snuffed out any stray sparks or embers. You are probably sensing a theme here; we really don’t want that round to go off prematurely from a stray spark. Tending the vent was so important Positions 1 and 2 had the authority to call out the Gunner and give the command “Tend Vent!” if they saw him slacking in his duties.

When Position 1 returned to the piece with the round, Position 2 would “tap him in” by banging the ramrod on the barrel. Position 2 was effectively saying that he had swabbed the barrel and that it was safe for Position 1 to step forward to load the piece. Position 1 would remove the round from the leather pouch and place it into the barrel. Position 2 would then use the ramrod to ram the round home into the firing chamber. Positions 1 and 2 would then take a step away from the howitzer.

Now Position 3 entered. Using a metal spike, he would pierce the round’s powder charge through the vent whole. This would ensure that the spark from the ignition cap would make it to the powder and ignite the round. Position 3 then placed a mercury fulminate fuse into the vent whole. Positions 3 and Gunner would then step away from the piece with Position 3 holding a lanyard tied to the mercury fuse. The Gunner then gave the command to “Fire” and Position 3 pulled the lanyard.

“BANG!”

References:

Inskeep, Steve. Imperfect Union: How Jessie and John Frémont Mapped the West, Invented Celebrity, and Helped Cause the Civil War. New York: Penguin Press, 2020, 60-63.

First Lieutenant Dyer, Alexander B. “The Army of the US Historical Sketches of Staff and Line with Portraits of Generals-in-Chief: Fourth Regiment of Artillery.” In Force Structure and Unit History Branch, edited by Bvt. Brigadier General Theophilus Francis Rodenbough and Major William L. Haskin, U.S. Army Center of Military History, 351-375. New York: Maynard, Merrill, & Co. 1896. history.army.mil/books/R&H/R&H-4Art.htm

"M1841 mountain howitzer." Wikipedia. Accessed July 23, 2022. https://en.wikipedia.org/wiki/M1841_mountain_howitzer.

A special thanks to the 2021 Historical Interpretation Team at Fort Laramie NHS. Ranger Joe primarily gave the Howitzer presentation. There were also Rangers Eric V., Steve, Clayton, Eric G., “Duke,” Eva, and Brenna.