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Discussion Starter · #1 ·
Hello to all, I've been a lurker here for many years. wIth the info here I finally built a bowling ball mortar. Grandkids love it!! I've shot it around 10 times so far and it shoots very well with 4 tablespoons of black powder. My breechblock measures 6" by 7" long with a 2"x2" powder chamber.. Thanks,
 

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Discussion Starter · #4 ·
The barrel is an oxygen tank, the breechblock and trunnion were provided by a machinist friend that is interested in the project . I'm using FG powder. The first shot of the mortar I used 6 tablespoons of powder and the ball traveled a few yards short of 1/4 mile. Could not see the ball land at that distence so backed off to the 4 tablespoon charge. The ball usually makes an odd whistling sound during flight. The deck boards on my porch are 6 inch so that may give a prospective of the scale.
 

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I like what you created. Looks good.

A few things for you to consider along the way of safety.

First you need to make capsquares. Capsquares go over the trunnions and keep the barrel from bouncing out of the carriage.

You need to get your self proper a powder measure and accurately measure your powder. Table spoons are for cooking. You need to be measuring in grains and ounces. Consistency is important for repeatability and safety. There is a indifference between a level tablespoon, a tablespoon and a heaping tablespoon.

A bit of terminology here. Your gun does not have a breech block, it has a chamber. A breech block is movable device that seals of the end of barrel.

We need to see some smoke and fire pictures.

Again, good job
 

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Discussion Starter · #6 ·
Thanks Double D, breechblock was a brain lapse,

I should have given more details concerning the charge, My wife had a handy dandy scoop marked 2 tablespoons, I measured the number of scoops in a pound of fg blackpowder and found that there were exactly 15 scoops(or 30 tablespoons) then divided 7000 grains in a pound by 30 and came up with 233 grains per tablespoon so my charge of 4 tablespoons would be 466 grains per scoop and 932 for the two scoops. I level off the scoop so I think my charge is repeatable.

I do have plans for the capsquares, the trunnions are deep set and tight and I thought that the trunnions would loosen up with firing but I guess I'll remove some wood and install the capsquares. I want to be able to repeatedly and easily remove them to separate the barrel from the bed for transporting and set-up as the outfit is fairly heavy now and my back isn't what it used to be. Any way I'm thinking of trying to find some studs with a wood screw on one end and machine threads on the other so I can take a few nuts off to remove the capsquares to separate.

Videos of the firing are in the works, I learning how to edit and I'll post some when I can.
 

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di1213 if your near a Home Depot they sell those wood screw studs on one end and machine thread on the other. They would work good in your application and would be easy to remove the capsquare as you intend on doing
Good job
Tino
 

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Discussion Starter · #9 ·
tino, yes a Home Depot is close, thanks.

flagman1776, I dip a .17 cal. cleaning brush on a short rod in a gallon water can, run it through the vent several times, then dip a tapered feather duster in the water and swab the barrel and using the tapered end to swab the weld area. then swab the powder chamber. Iuse a rag to then dry any excess. I use a funnel with an extension to drop the powder. I start the ball then let it drop. Then insert the fuse. I'm careful to keep my body away from the barrel as much as possible. Is there any advantage (safety or otherwise)to placing my charge in a thin aluminum foil packet then drop the packet in the chamber?
 

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The cleaning brush is good. A stiff brass "pick" is also a good idea... Mine has a 4 sided point to assist in clearing the vent.
I like a paint roller on a stick for my mops. I took a caliper to Home Depot to find the right size. Don't need a rammer...
Mortars are operated similarly to other cannon... the funnel with extension is the right way to load a mortar. The foil is useful to keep a charge together in a Horizontal tube but not particularly useful in a mortar unless you want to premeasure charges. But if you use foil, you'll need a worm to remove foil remants after firing.
Knowledgable mortar folks use a piece of steel plate to block the vent blast when firing. Vent blast can be quite dangerous.
Kudos for safety. You are on the right track. Always safety first.
 

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After seeing some BB mortars I believe you have made a nice light tube that shoots BBs .

Nice and big so you can see the ball in the air AND finding it latter ,never mind the whistling sound !
Good job !

Gary
 

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I have to add that I think your trunnion is a little on the small side, diameter-wise. The wide cheeks are a good compromise and the relatively light charges also help, but I think it will bend with continued use. If you would add a third pair of cheek pieces close in to the chamber piece, you would reduce the tendency toward bending. They don't even have to be full length. And make sure the area of the cheeks under the trunnion is firmly seated when you fire so the recoil force goes directly into the ground instead of being supported by the ends. This will prevent breaking under the trunnion cuts.

The whistling is caused by air flow across the finger holes as the ball rotates in flight; like blowing across the top of a bottle. You can stop it if you like by putting a piece of tape across each hole. But I like the whistling.
 

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Discussion Starter · #13 ·
http://smg.p. EDITED.... looks like the video doesn't work so I'll try gain later.....

Maybe this video will work..........

George, the trunnion is 2" diameter and there is 2" of the unsupported trunnion between the powder chamber and the bed.

If the video works it will show a shot yesterday. My shooting areas are limited, I had to shoot on a very isolated but a very trashy field. I inserted a smoke bomb in the ball and ignited it before I shot,( rained that morning so no danger of fire) I would never have found the ball otherwise.

Thanks to all for the comments and recommendations.
 

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Discussion Starter · #16 ·
Thanks Double D. The smoke bomb is a commercial product that has a short fuse. Rather than trying to light that fuse while in the loaded barrel( not ready to be a Darwin winner yet) or using a very long fuse , I taped an electrical igniter to the fuse and lit it off before the mortar was fired. The igniter gives some smoke and the fuse taped beside it will add to the smoke giving that first puff. Then the fuse burns down to the smoke bomb and after the smoke from it starts billowing, the mortar fired.

https://youtu.be/WlCTREVnzME
 
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