Charge/Chamber sizes for Bowling Ball Mortar

[DH2]

Greetings all! I've been browsing the forum recently in preparation for constructing a bowling ball mortar that follows the coehorn pattern. I've got some questions for those who know more than me.

What size charges are safe and appropriate for launching bowling balls? I've heard of everything from 200 gr to 3 oz and would like a little clarification as to what is actually safe/appropriate.

Hand in hand with that question comes this one: when you bore out the chamber for your bowling ball mortar, how large to you make it?
I was thinking of making the chamber just large enough to hold the 'maximum' charge (meaning the largest ill ever shoot, not one close to the actual maximum that the mortar could take)

What are your recommendations?

[dan610324]

do you got any drawings on the design ??
an exact scaled replica ?? or just similar in style

cast iron ??
cast steel ??
cast bronze ??
machined from solid bar ??
other method ??

if you add some more info Im sure there are people here who could give you some guidelines

[DH2]

I'm intending to use steel for the breech, I dont know what kind of steel yet, and to be honest, it might be whatever scrap I can find at a junkyard. The dimensions that I've figured as of now was trying to find a piece about 6" in diameter, and about 5" long. Just making up numbers, I was intending for the powder chamber to be a hole cut 2" in diameter and 3" deep. I figure that that would be close to 3 oz of ffg BP.

[dan610324]

it wouldnt be much of the design that remains from the original coehorn design then
as the barrel should have approximately 8" inner diameter if I remembner correct
or was it 9" ?? well not sure of that , probably 9"
the bore would be 22,5" deep + the powder chamber if the coehorn have 2,5 borediamert deep bore
I think it had those proportions
where to place the trunnions , and how to attach them ?
if you are going to use unknown steel its not safe to weld

please try to show a sketch of how you have been thinking
dont need to be any fancy cad drawing , just take a paper , pencil and a ruler
this is interesting

[DH2]

Well I'll admit that I said 'coehorn' to differentiate from 'stokes' and therefore avoid the ire of the atf. The best example of what I'm trying to do is basically the Florida Mortar (http://www.gboreloaded.com/forums/index.php?topic=28013.0) with a 6" diameter breech instead of a 4" and a touch hole instead of a slap hammer and primer.

I'll try to get some drawings up when I've got access to a scanner.

[Cat Whisperer]

DH2 --

WELCOME to the board!

Suggest using 1018 to 1024 for the powder chamber.  Mild steel.  It takes the abuse of repetitive firings. 

Often available from machine shops - the ends of the longer rods are cut off and become scrap.  Also the ends are often discarded.

Using a numbered steel gives you the confidence in the material where it's most critical.

[DH2]

Thanks for the welcome! I'm glad to be here.

Thanks for the materials suggestions. I'll be sure to start looking for some.

What tends to be the usual powder charge for lobbing bowling balls?

[1Southpaw]

I use 1.2 oz for 100 yards  , 3.5 Oz @ maximun full chamber for 700 yard shots.  
My chamber is 1.55 dia and about 3 " deep.  Should write this stuff down some place I can recall  
I turned the chamber on an old SB lathe and welded it to a 1" base plate .  Rather shoddy looking but works .  The tube is a piece of oil field casing . Scrounged for free from a drilling company .
I'm happy with the outcome and looks of the beast .  My avatiar is the BB mortar in fresh paint.
Edit: FG powder is used .

[dirtdobber1919a4]

gents, i finnaly fired my bowling ball mortar a few weeks ago. 16 pound ball with a 2 ounce charge of Fg went about 1.5 miles.  a  buddy of mine did the math  to figure it out. it was launched at a 60 degrees and a conservative guess of 450 fps.  so beware.  barrel is made of an argon tank.

[BoomLover]

dirtdobber, is that a measured 1.5 miles? As in 7920 feet? 2640 yards? And a 2 oz charge? Incredible!!! So, when do you go into mass production? LOL...with those results, some bowling alleys are going to be looking for their balls! BoomLover

[Double D]

I'm with Boomj, how do you know it 1.5 miles, is that where you found the ball?  Or did you calculate it\, what numberd di you use to calculate it.

There is a story told that a bowling ball was found 1.86 miles from where a mortar shot it last summer, but that was with a pound of powder.

[smokemjoe]

What is the bore size on your tubes, I will be ordering a tube that has a bore size of 8.750 and ball size is 8.563 and 8.500, Thats what the BB sizes are, Thanks-

[BoomLover]

Double D....had your glasses checked lately? LOL...Just giving you a hard time, here on April 19...Patriots Day! I'll be firing at least two of mine today, in remembrance! From BoomLover, not BoomJ

[Double D]

Double D....had your glasses checked lately? LOL...Just giving you a hard time, here on April 19...Patriots Day! I'll be firing at least two of mine today, in remembrance! From BoomLover, not BoomJ

I refuse to confirm this rumor at all, about the ball going 1.86 miles on a pound of powder, not that I need new glasses, that is fact!

Here is the information about bowling balls for mortars from our reference sticky.

A bowling ball gun with proper windage would need a minimum bore of 8.815 inch.
Circumference of a bowling ball.  Max 27.002 inches.  27.002 xi .31831 = 8.595 maximum diameter of a bowling .  (8.595/39)x40= 8.815 inches http://www.topendsports.com/sport/tenpin/dimensions.htm

The dimensions of the powder chamber are going to be  determined by the O.D of the barrel.  There is no need in a recreational mortar to make a chamber capable of throwing a ball further than the safest greatest distance available to you to fire.  I'll  go even further and state if you can not see the mortar ball during its entire flight, it is unsafe, unless you have an absolute 100% controlled access to the Impact zone.  Private property and no trespassing signs are limited access and not controlled.  If you can not see the impact zone, you are negligent to fire.  

Beside half the fun is to see the impact.

[BoomLover]

I do agree totally! BoomJ....I mean, BoomLover.....LOL

[Cannoneer]

Double D....had your glasses checked lately? LOL...Just giving you a hard time, here on April 19...Patriots Day! I'll be firing at least two of mine today, in remembrance! From BoomLover, not BoomJ

All right, BoomLover, just what do you find so offensive about being mistaken for me!

No need to answer, BoomLover, the above was intended as a strictly rhetorical question.   How's that for playing it safe?