Cohorn mortar

[Bill Smith]

I have what appears to be a solid cast iron shot, 4.81 inches in diameter, 16.4 pounds. There is a mold seam (barely visible) , no other markings. The specifications I have seen for a Coehorn mortar are a 5.82 inch bore, 17 lb shot. Could this be a Coehorn round?

 

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[SkaBa]

Pics, please.

 

[Bill Smith]

Thanks for your reply! Sorry, but I'm not able to send photos. There isn't a lot to see...just a round solid iron ball, some corrosion. The mold seam is very faint, and would probably not show up in a picture.

 

[ARC]

Size and weight are off...
?

 

[Bill Smith]

It's confusing to me. From what I have read, the CSA used 12 pounder and 24 pounder Coehorns mortars, but there is also a listing for a model that had a 5.82 inch bore, firing a 17 pound ball with a 1/2 pound of powder. The ball that I have is 5.81 inches, although that is not absolutely precise. It weighs 16.4 pounds, after some loss of metal due to rusting and pitting. It was inherited from a digger, along with an assortment of other balls and shells, but the exact provenance of any one of them is not known. It could just as easily be from a ball mill rock crusher.

 

[TheCannonballGuy]

The Coehorn Mortar's bore diameter was 5.82 inches, but it is a muzzle-loader cannon (the ammo is loaded into the gunbarrel's front, not its back end). Therefore, a cannonball for a Coehorn has to be about 1/8th-inch smaller than the bore diameter... in other words, approximately 5.70-inches in diameter. But you say yours is 5.81" in diameter. Your size-measurement might be a little "off" due to rust/dirt encrustation on the ball.

You said the ball is a solid (not hollow) one. But a 5.8"-diameter solid ball made of cast iron should weigh a few ounces more than 24 pounds, not the 16 or 17 you report. That indicates the ball is actually a hollow shell, not solid. Are you absolutely sure there is no fuze-hole in it?

Go to www.civilwarartillery.com/shottables.htm to check the weight of a 24-pounder (5.82"-caliber) Solid-Shot and a 5.92"-caliber hollow shell.

 

[Bill Smith]

Thanks for your reply!

Sorry, I used the wrong number for the shot diameter. The Shot is 4.81 inches. The listed bore for the "24 pounder" mortar is 5.82. My shot is 16.4 pounds with a little weight loss due to rust and pitting. The actual listed weight for the 24 pounder Coehorn shot is 17 pounds. I guess the classification was nominal rather than exact. The ball that I have has no provision for a fuse.

The Coehorn mortar was designed so that it and its carriage could easily be picked up and carried from place to place by 4 men. It could be quickly deployed and then moved after a few rounds, which would make it more difficult to find and destroy. It only used half a pound of powder, perhaps not being robust enough to handle more. An actual 24 pound shot might have been more than it could deliver. The effect may have been more psychological than tactical. A lot of "if's" and "maybe's".

 

[TheCannonballGuy]

Thank you for providing a corrected size-measurement. That makes your size and weight measurements match up... which enables me to definitely identify the ball.

If you check the final chart at the link I gave you above (www.civilwarartillery.com/shottables.htm), you'll see that a cast iron ball which weighs EXACTLY 16.0 pounds will be 4.924 inches in diameter. Although your ball is .11-inch smaller than that, it is heavier by almost half-a-pound. Therefore, your ball is made of steel, not cast-iron, and thus it is not a cannonball. (There is no Historical record of steel cannonballs ever being made or used in the United States.)

Because your ball is steel, AND it shows a mold-seam, it is most likely a Mining-&-Stonemilling Industry ore/rock-crusher ball, known as a Mill-Ball. Because all a Mill-Ball does is crush rocks, there's no need for the ball's manufacturer to pay for the labor of removing the casting-mold seam from the ball's surface. Balls which are used for "more-complicated" purposes (such as a check-valve ball) do need to have their mold-seam removed.

Almost forgot to mention:
Army artillery mortars never fired Solid-Shot balls... because the only thing a Solid-Shot fired from a mortar would do is make a small round hole in the ground where it landed. Only explosive shells were used in mortars.