OXYGEN CYLINDERS AS BOWLING BALL MORTOR - SAFE??? & HEL

[IAMACLONE_2]

Just built, not test fired, a bowling ball mortor made out of a 110cuft Oxygen cylinder.

First step was to have the Oxygen cylinder pressure tested, that has been done. Rate tested @ 3750psi.
 
Cylinder wall thickness at the bottom (muzzle) is apx.  .375" or more.
Bore size ID is 8.250"
Neck thickness of the bottle is apx. .675" thick.

We have drilled and taped a 3/8" pipe plug thread fuse hole about 2" above the top of the neck.

Have had the bottom cut off of the cylinder.
Made a base plate out of 1/2 steel plate 2ft square.

Bought a forged steel trailer ball in 2 7/16 with a 8,000lb Bulldog coupler welded to the dead center of the base plate.
The 2 7/16 ball is threaded into the neck of the oxygen bottle.

Intend to use Pyrodex  35 & or 50 gr.  for propellant, and cannon fuse for ignition.

Found out today that most bowling balls are 8.75", bummer!
So now have to find some type of suitable ammo.

BUT THE MAIN THING!
DOES THIS SOUND SUITABLE & SAFE TO SHOOT?
GIVE ME SOME HINTS & FEEDBACK, PLEASE!!!!

Thanks
Walte

[John N]

I remember an earlier thread about a bowling ball mortar and this good piece of information from Double D:

Circumference of a bowling ball. Max 27.002 inches. 27.002 x .31831 = 8.595 maximum diameter of a bowling ball. Bore diameter (8.595/39)x40= 8.815 inches http://www.topendsports.com/sport/tenpin/dimensions.htm

The second figure of 8.815 inches for the bore diameter is based on a maximum diameter bowling ball plus 1/40th of the ball's diameter for "windage".

[IAMACLONE_2]

My major concern is this thing safe to shoot, without bursting!

I expect to use the 35gr pyrodex pellets & shooting a soccor ball for the first test.

Then work my way up on weight of projectiles & the amout of pyrodex to use.

May end up using foam as a sbaot's and the small 6inch dia. Skee balls as projo's

Walte

[Double D]

First yes it might be safe, but more importantly from your description, may be illegal.

Building the tube with a base plate and bipod makes it a replica of a Stokes mortar. The Stokes mortar was not invented until around 1914.  Becasue it was invented after 1899 any replicas of it could be considered a destructive devices.  

I am aware of at least two cases where persons with these type of homemade stokes mortars have been arrested.  Of course they were doing other bad things like running meth labs or and holding hostages.  

none theless we do not want this board to become the pleace for rookie ATf Agent to come and harvest leads to my cases.
 
The scope and focus of this board is antique black powder mortars and cannons and there replicas, made in the spirit of the National Firarms Act antiques rule.

Any further discussion on the topic must first be on finishing your gun out so it is a replica of an antique.  

Any other discussion will be blocked or deleted.


What you need to do is figure a way attach trunnions. Then build a bed for it similiar to what Bill Tyrell built.  We have pictures of his gun on the board some where.  Ii will find them and post a link.

[CAV Trooper]

Have you thought about trying real black powder instead of Pyrodex pellets? Or, if you really want to use Pyrodex, try lose powder instead of pellets. IMHO you'll probably get much better results.

Since the pellets are really designed for in-line rifles it may be tough to light one with a fuse. I know that there can be ignition problems in flintlock and percussion rifles when you use pellets.

With BP, you actually push the fuse into the powder and ignition is virtually assured. With pre-formed Pyrodex, the end of the fuse would rest against the side of the pellet. Will that cause ignition every single time? Don't know for sure but I would rather not chance it.

Maybe it's just me but I REALLY hate when you load it, light it and it doesn't go boom. Gets the pucker factor up to about 12 on the Richter scale when you have to unload the thing and start over.
 
I'm not quite sure from the description of how you built the mortar if there's a powder chamber. If there isn't, do you intend to just have the powder (or pellet) loose in the bottom (formerly the top) of the cylinder? Without a powder chamber, it may not be safe to shoot at all. Both BP and Pyrodex can produce pressures way beyond 3750psi.

[GGaskill]

I have seen bowling ball mortars made from high pressure gas cylinders but they were special extra high pressure (6000 psi, 3/4" walls) cylinders, not the ordinary ones used for shop welding gasses.  I have seen them fired with as much as a half pound of cannon grade black powder without difficulty (except to the carriages.)  You must remember that even a 16 lb bowling ball has an extraordinarily low sectional density.  They were configured in the style of the M1861 siege mortars (the breech end is hemispherical.)  One of the carriages was made of 3/4" plywood in a shape resembling the M1861 carriage and was quite effective.

http://www.cwartillery.org/ve/mtr10sg61.jpg">


I would not waste my time with Pyrodex pellets.  In my early days of black powder artillery, I used Pyrodex (and in the early days of Pyrodex, a cannon grade was offered.)  I ran out one day and substituted all black powder (an equivalent charge) and found that I got twice the boom and twice the range as I was getting from Pyrodex.  Same thing with smokeless.  The pressures developed in BP artillery do not let the smokeless burn efficiently.  A friend who was using a mixture of smokeless (leftovers from countless cartridge pulls) and black would get a lazy flame from the muzzle of his gun after each shot; it was the smokeless still burning after the shot was long gone.  It is possible to blow up a BP Artillery piece with smokeless but it would require large quantities and heavy shot in large bore pieces (not so much in small bore pieces.)  Use of smokeless in amateur artillery is not a good idea.

[IAMACLONE_2]

Per BATFE Branch Tech Dept spoke with them prior to build and faxed them a set  blueprints, for verification.

You just cant be to sure these days, its allways best to ask first, when dealing with the BATFE boys.
 
My build is within the scope of "antique blackpowder weapons" are are exempt from the NFA act of 1934 & GCA of 1968, per BATFE Branch Technology division..
 
A letter from the BATFE, showing such approval and their decsion can be provided upon your request.
 
Just dont want to get sideways with you guys. Just being honest and straightforward.

I'm also a 25yr plus owner of various registered NFA weapons.

Thanks
Walte

[Double D]

Great hang onto that letter and if you don't mind could send me a copy, I would like to look at it.  Perhaps we can figure a way to post it in our FAQ's and protect your identity.

You won't get crosswise with us here on this board building a bowling ball mortar.  We are more concerned about you getting crosswise with the law.

We also seem to come under a great deal of scrutiny here. Because of that we carefully and strictly guard  this forum against any appearance of impropriety.  We want this board to be a place where we can get together and share ideas about our hobby and not one where we are constantly getting sniped at.

[Cat Whisperer]

Per BATFE Branch Tech Dept spoke with them prior to build and faxed them a set  blueprints, for verification.

You just cant be to sure these days, its allways best to ask first, when dealing with the BATFE boys.
 
My build is within the scope of "antique blackpowder weapons" are are exempt from the NFA act of 1934 & GCA of 1968, per BATFE Branch Technology division..
 
A letter from the BATFE, showing such approval and their decsion can be provided upon your request.
 
Just dont want to get sideways with you guys. Just being honest and straightforward.

I'm also a 25yr plus owner of various registered NFA weapons.

Thanks
Walte

I can see DD has already expressed interest in seeing the letter, as am I.

SO, Let me say WELCOME IAMACLONE_2 to the forum.

It is always exciting to hear of folks getting into mortars for the first time and you have certainly taken a very responsible approach to a subject that has potential of accidently getting legally burned.

To address the original question of safety lets examine the process of firing black powder.

As with smokeless powder there is a sharp peak of pressure - early on in the event.  If you have a strong container (powder chamber) coupled with minimal air space to a larger chamber containing the ball, you have contained the burn during that first part of ignition where the pressure spike is contained by a very strong container.  THEN as the ball moves down the tube with expanding gasses pushing it the pressures are much lower and the need for strenght is much less.  That is the principle of the Coehorn design.

Hence, the questions you received on how it's built - powder chamber and so forth.

Obviously wtih a coarser powder the burn will be slower than with a finer powder - it's a matter of surface area burning - which grows less and less as the grains burn.

There are a few folks here that have put together bowling ball launchers - with luck you'll get a response or two from them soon.

Again, welcome, be safe, legal and have fun.

[Cat Whisperer]

Let me add a  little bit more to the collection of miscellaneous information.

On each cylinder is a number which defines the pressure test it underwent - the folks at the welding supply shops can tell you what they mean.

I just measured my cut-in-half 02 cylinder.  8.55" diameter about midway with just over 1/4" thick walls.  Don't know the pressure rating, but I'll find it out.

Then I measured 4 bowling balls.  FOUND ONE at 8.52 the others at 8.55, 8.56 or slightly larger.

Windage (clearance) is one of the keys to keeping pressure low.

[IAMACLONE_2]

Double D & Cat Whisperer - All of my post are from work.

Will scan the letter & e-mail responce from BATFE Branch Tech Thursday morning.

I know your concern, been there done that many times while building on Form1's

I think you guys might be right on my choice of cylinders, will check with my bottle supplier on spec's.

Thanks Again
Walte

[Cat Whisperer]

walte -

That's right-much kind of you to share that information.  I think I understand the process of Form 1's - build it and submit for approval?

This sounds like another FUN project.

[Blaster]

IAMACLONE-2.... I just sent you a PM regarding a BB mortar.  Thanks.
Blaster (Bob in CO)

[CAV Trooper]

I think I understand the process of Form 1's - build it and submit for approval?

CW,

I think you have that backwards. You have to get the Form 1 approved FIRST and then build. Creating an NFA weapon (like a short barrel rifle for example) without getting the approval to do so in advance would put the builder in violation. Bad juju.

[Cat Whisperer]

I think I understand the process of Form 1's - build it and submit for approval?

CW,

I think you have that backwards. You have to get the Form 1 approved FIRST and then build. Creating an NFA weapon (like a short barrel rifle for example) without getting the approval to do so in advance would put the builder in violation. Bad juju.

Yea!  I knew it had SOMETHING to do with building and getting approval as opposed to transferring from one to another owner.