Home-Made Mortars

Homebuilt Coehorn mortars are inexpensive and just super cool. Any three-thumbed ape
can manage the necessary carpentry to build one up at home.

The Internet revolutionized the way people in developed countries live their lives. Where previously clever jokes, eccentric fetishes, and quirky hobbies just smoldered along in obscurity, nowadays thanks to the Internet adherents of all manner of manifest weirdness can connect with other like-minded souls. The gear to stoke all these odd pastimes is never more than a click away.

For me it really doesn’t matter if it is a Daisy Red Ryder spring-action repeater or a vintage German assault rifle costing more than my car. I seem always at my happiest turning ammo into noise. While you can drop some truly obscene amounts of cash on stuff black, old and oily, there are also a few places where you can still substantially enhance a proper gun collection without squandering Junior’s college fund or hocking a kidney. The lonely corner of the shooting sports we will explore today is DIY homebuilt artillery.

The smaller of the two mortars fires golf balls.

The Coehorn Mortar

Baron Menno van Coehoorn was a Dutch military engineer who lived in the 17th century. A master of siege warfare, the good baron developed the high trajectory mortar that sort of bears his name. Realizing fortifications of the day were designed to withstand assault in the horizontal plane but not in the vertical, Coehoorn contrived a relatively lightweight gun that would throw explosive projectiles in a high arc up and over conventional fortifications. Over time his surname was Anglicized to Coehorn.

While these mortars were used sporadically in various European conflicts, they really came into their own during the American Civil War. Union forces employed 12- and 24-pound versions (so named based upon the weight of the shot they fired). Confederates crafted their own 24-pounders out of rough iron. These guns were mounted on fairly simple wooden carriages that could be manhandled into position by a typically three-man crew.

The shells they fired were hollow balls filled with black powder and ignited by a time fuse. Elevation was fixed so the range was adjusted by cutting the lift charge. The 24-pounder could theoretically fire a 17″ shell up to 1,200 yards, though practical ranges were generally shorter. Coehorn mortars used during the Civil War were impossible to defend against and served as terror weapons during that horrible conflict.

Modern Home-Brewed Examples

The barrels come from www.blackpowder-cannons.com. They offer a variety of fascinating DIY gun projects, but their Coehorn tubes come in two flavors. The 1.75″ version shoots golf balls. The larger 2.625″ gun throws aluminum beverage cans. These two barrels will set you back $55 and $100, respectively.

The barrels are formed from modern steel, and the workmanship is superlative. Load data is engraved upon the larger gun. The barrels are drilled to accept standard waterproof cannon fuse available from a variety of sources.

You will need to craft your own carriage, but that makes for a great Saturday afternoon workshop project. Schematics and plans are available online, and the barrels also come with plans of their own. I opted to build one utilitarian and another more period correct. The end result will spice up anyplace two or more gun guys are gathered.

Crafting your own simple carriage is a breeze with basic hand tools.

The Build

Anyone even reasonably handy with tools can conjure the carriages. Power tools certainly make the project easier, but our Civil War forebears did just fine without them. Nondescript pine lumber renders fine service as raw material.

The overriding consideration is to make this thing strong. Recoil, particularly on the larger version, is prodigious. Once I got everything finished up I drilled holes crosswise against the grain and glued lengths of dowel in place to keep everything rock solid. Sand everything smooth afterwards, and the dowels don’t show.

Lag bolts or long screws keep it all snug. The only real technical challenge to the build is mounting the trunnions. You can cut the holes with a hole saw or spade bit. Short lengths of brick strap or steel stock will hold the trunnions in place. Your local building supply store will have the steel stock in ample quantities. I cut my steel pieces out of an old computer case. A drill press makes the holes easier, but a hand drill will also suffice.

I put dowels in the side of the larger carriage to make it easier to tote. It is theoretically possible to build a wedge or something similar to adjust the elevation, but cutting your lift charges and adjusting the fall of shot is half the fun. Once everything is shaped and sanded to your satisfaction stain it with something dark and smoky to complete the period effect.

Ammunition

The smaller gun shoots golf balls. I don’t play the game myself, but a trip out to the local course for a meeting with the groundskeeper bought me all the practice balls I could ever use. These guys gather old balls up and sell them on the side for a little spending cash. $20 got me a bag full.

I built a wooden monkey to hold a handful of golf balls in a pyramid just because it looked cool. Make the internal dimension 4 and 7/8 inches on each side, and fourteen golf balls fit perfectly. Once appropriately stacked this makes a simply splendid addition to the man cave. The carrier is just as portable as the gun should you wish to tote it to the range as well.

The larger gun is bored to accept aluminum beverage cans. The unopened liquid-filled versions run fine, but I choose to fill discarded cans with sand. I didn’t want to run the risk of firing an unopened can of soda and inadvertently drenching my gun in sticky beverage. When the kids were young they enjoyed the task of filling the cans, and the resulting projectiles are nice and beefy. Unlike your favorite black rifle, ammunition is essentially free.

There is a powder well machined into the base of the tubes. A long funnel gets your powder where you want it.

Feel the Power

So what is it really like to touch off one of these little monsters? The golf ball version will quite literally throw a golf ball out of sight. In fact, I’m not sure these things ever came down. I’ve yet to find one.

The Coke can version is a freaking mule. The thump on firing hits you in the chest, and the heavy can will sail well into the next time zone. Muzzle flash when fired as dusk will inevitably induce the giggles.

The concave bottom of the can forms a nice gas seal. For reasons I do not fully understand both of these guns perform better with black powder than with Pyrodex. Black powder can be tough to find these days, but Pyrodex is still pretty cool.

I have found countless fired Coke cans filled with sand downrange during my strolls through the woods on my small Southern farm. The skin is invariably wrinkled from the stresses of launch and reentry. Bauxite, the ore from which elemental aluminum is derived, is the eighth most common material by mass in the earth’s crust, so it’s not like it’s actually littering. Additionally, if the ground is soft and there are no intervening trees they will likely bury themselves.

Practicalities

These two homebuilt Coehorn mortars have no practical applications beyond spicing up your golf game. You’ll not use them for home defense, and you’d be better off with a proper baseball bat if you spot zombies staggering up your little cul-de-sac. These nifty little cannons are range toys pure and simple.

However, don’t let the term range toy mislead you. Both of these guns are profoundly powerful. “Blew his head off with a golf ball” would look pretty stupid engraved upon a tombstone, so be careful. The Coke can version would easily drop an elephant.

There are powder wells machined into the bottom of the barrels. You can just dump your powder in and get decent results. However, I use a long-necked funnel to make sure every grain gets where it needs to.
Be generous with the fuse, it’s cheap, and wear the standard safety gear. Give yourself plenty of time to get a safe distance away before the gun goes off. The anticipation, particularly if there are kids involved, adds to the excitement. Be meticulous about mopping out the bore between each shot to ensure no smoldering embers remain.

Cleaning any black powder gun is important. The propellant and fuse are full of all manner of vile corrosive stuff, so a bit of warm soapy water is in order at the end of a fun day at the range. If you build the carriage such that the barrel is easily dismountable you can just tote it to the sink. Dry everything out thoroughly afterwards and coat it with a nice film of oil. Be mindful of the flash hole and mop out all the oil before you attempt to shoot it again.

Both of these mortars are incredibly impressive on the range. However, as they load from the muzzle and are fuse-fired there are no federal restrictions on building, owning, or shooting them. If your particular locality has an ordnance preventing such stuff as this you should move to someplace less lame.

The golf ball mortar takes up little space yet produces outsized fun.

Ruminations

Yours may be a truly epic gun collection already. You may have Patton’s ivory-handled revolvers and Han Solo’s original DL-44 blaster hanging on your living room wall. You might even own the very 1873 Colt Peacemaker than Moses himself had strapped to his hip as he led the Israelites out of Egypt and into the Promised Land. Even so, chances are you don’t have anything quite like this.

For less than the cost of taking your family out to dinner and a movie you can craft the most remarkable range beast with nothing fancier than hand tools and a little time. The end result offers a splendid sense of accomplishment and is just crazy fun. There’s little in this odd quirky hobby of ours offering as much bang for your buck as a homebuilt Coehorn mortar. What are you waiting for?

For more info: http://www.blackpowder-cannons.com