Mortars

I have a question how many of us play with mortars, am i the only one here, that shoots one.
I do blank fire at civil war events and get to do live fire at 2 events a year(lost 5 mortar balls this year $80 each).

I know this is about cannons but they are all artillery pices in the end. Hope I am not treading on any one toes.

There are a couple of groups here in Indiana that have and fire mortars at events that you could contact on facebook.

I've a repro, brass, 18th century Cohorn.

LD

I have a beer can bored Coehorn. Max range seems to be about 400 yards with beer cans full of concrete. All I can say about accuracy is that they do land in front of the muzzle.

My mortar is 24 pound 5.8in bore coehorn, made out of bronze,on a wooden base. range appox 1/2 mile with 8 ounces 1F powder or appox 100yards per ounce of 1F.

Just be sure to use black powder, pyrodex does not work :redface:.

Loyalist Dave said:

I've a repro, brass, 18th century Cohorn.

Click to expand...

I once watched morter fire at a NSSA skermish at Fort Pulaski. All morters were iron except for one Reb unit that had one of brass. That thing would ring like a church bell when fired! Kinda neat.

I have built several mortars loved shooting them. Built a 12 pounder when i was in school gave it to my instructor as a thank you. Kicking my self now since i cant make one that big on my lathe. Would shoot them with my friends and see who could hit closest to a surveyors flag.

Fwiw, when I lived in Washington DC & was the Brigade Commander of the local SCV Brigade, I was the sole person, who was authorized by the DC City Council to fire artillery in DC, other than the US military services.
(Of course, ONLY blanks were fired at SCV Memorial Ceremonies.)

In those days, I often had reenactment CS Artillery units that fired "full-scale mortars" for those ceremonies.
(At least 5-6 of those artillery units had mortars of various bores, so I presume that mortars are not rare in reenactment units.)

yours, satx

I've had a lot of fun with a bowling ball mortar I made with a cut off oxygen cylinder.
It will shoot roughly .5 mile or so and it rings as well when fired.
I mounted it on an a glue lam and iron sled base that has a screw elevator that will traverse from about 20 degrees through vertical.
It is striker fired from a musket cap with a twenty foot lanyard.
I found that the oxygen cylinders are made from seemless 4140 chrom-molly steel and are nearly a half inch thick in the base cup tapering to a minimum wall thickness of .3125.
Proportionally the wall thickness is as great as a shot gun barrel used with smokeless powder and made of the same material, stress relieved 4140 chrom-moly steel. The cylinders are however drawn not bored as a shotgun barrel would be but then the pressure levels are less with BP.
Still,when firing I always keep it 75 yards away from any by standers and use a lanyard extension to discharge it.
1500 grains of Cannon grade will lift a 16 lb ball to just about out of sight with over a 16 second flight.
I did shoot a six inch Birch tree off at over a hundred yards once by accident. :rotf:

When HP cylinders are hydro tested they are tested at 1.4X their working pressure. They must return to within .03% of their original volume in order to pass their hydro test. I believe HP T cylinders come in several pressure ratings; 2400, 3500, 4500, and 6000 psi. Generally, the neck is thicker than the walls, which is where they fail if they're going to catastrophically fail. What you're describing probably doesn't have a muzzle swell, which lends strength to an area that can't "borrow" it from metal forward of it.

Most HP cylinders are good for 100M+ cycles before metal fatigue compromises their integrity. But, generally speaking, if you're running or distancing yourself from the piece after lighting the fuse, that means that you don't have total confidence in the integrity.

Have you done any calculations on your pressures? Be careful. We don't want to read about you in this year's Darwin awards.

No, I never fully trust anything like this when used for application other than designed.
The steel type though is gun barrel alloy (4140 annealed) and is not welded any where.It is draw and as such means it has been annealed several times in the drawing.
A bowling ball is actually quite light as a mortar projectile. A full size Cohorn shell weighed over 40 pounds and the tube was wrought iron.
This mortar tube is far stronger and more ductile than the originals were.It is also shooting less than half the charge and less than half the projectile weight.

The real danger is in the loading as the ball has to be delivered down the bore and nested on top of an inner powder cup I machined that threads into the neck from the inside. It is double walled at the very base because of this cup.
I like to wait a full five minutes between loadings and never use any kind of wadding to make embers.
I also developed a loading sling that takes advantage of the finger holes in the ball so the ball can be seated without exposing your arm or hands down bore.
It is loaded from the side of the muzzle,lowered to the powder cup than a collar is raise with a draw string from out side the muzzle releasing the wood pegs from the finger holes. The loading harness can then be withdraw from the tube.
Makes me feel much better about loading the projectile.
I do use several orbits of heavy vynle pipe tape put on the ball mid-drift, for a snug slip fit to the bore as a gas seal.
I don't know that a meaningful calculation as to breech pressure could be made without a strain gauge to actually measure it.

Without proper testing equipment, I would then defer to the N-SSF safety guidelines, or those published by the American Artillery Association. Otherwise, maybe you could somehow duplicate the procedures used by the European proof houses for small arms, with special emphasis on safety. If a small arm catastrophically fails when something goes wrong usually it's a finger or hand that's injured. When an artillery breech fails it kills the whole gun crew. If you don't want to go through the hassle of all of that, I will ask my mother in law if she's available for some destructive testing.

I won't ever sell it that's for sure. When I get to old to wrestle it around I'll disassemble and hall her off to the scrap metal yard.
It sure is fun to shoot though and I still have the folks at the yearly Territorial match ask me to bring it.
We just moved to a smaller range this year on a private farm and I don't have room enough to fire it any more.