Chamber pressure of a beer can mortar

[BMG]

Does anyone have an idea of the chamber pressure of a beer/soda can mortar.

[Double D]

There are a lot of "Depends" in that question.

Depends on the weight of the projectile.

Depends on the diameter of the powder chamber.

Depends on the burn rate of the black powder used.

Depends on the quantity of the powder used.

You will need to take pressure gun readings for a definitive answer.

But if you just want to shoot your beer can mortar safely and have some fun follow the safety quidlelines for determining loads laid down by N-SSA and or  AA.

If you are really interested acquire Matthew Switlik's book  The More Complete Cannoneer and build the pressure transducer found in the book and do your own testing.   

[Cat Whisperer]

BMG-

WELCOME to the board!

DD summed it up.

When I built my first one, I knew NOTHING about how safe it would be.  Fortunately I turned it from a solid billit of HRS (hot rolled steel - very tough and strong, mild steel which is good).  I turned a powder chamber in it with rounded inside corners for strength.

THEN when I first fired it, I filled the cans with water.  That is a LIMITING factor.  When the pressure from underneith the can presses too hard on the bottom it presses the sides out.  So the first indication of brining the charge up in pressure is scrape marks on the can; the second indication is that the can splits and doesn't go anywhere - just sprays water all over.  Both were MILD loads.

Learning of strengths of steels and such, I then filled the cans with sand or concrete - greater mass/density and hence greater range - but with no indication of pressure.

In general, in mortars, pressure is much like that of a shotgun - much lower than that of a rifle.  But design-wise follow the examples of successful designs, make a little stronger for insurance and build it.

Powder chambers are good.  Rounded inside corners are good.  Good quality steel is good.  REASONABLE powder charges are good.

[Artilleryman]

To add to DD remarks, windage makes a difference also.  The limiting factors that tend to keep pressures down for the N-SSA are: you are only allowed a maximum shell weight related to the caliber of the mortar, you have to maintain at least a .010 windage, a maximum elevation of 60 degrees, and we only shoot to 100 yards.


 

[irishman]

Where does the projectile (beer can 2.605) divided by 39 times 40 come in? All of the prints I have are calling for 2.625. The bud can would require 2.672. .047 = a different personality

                                                   Michael

[Double D]

Michael,

Do you have the old 1970's beer can plans for using the old steel beer cans that required a chucrch key to open?

Just modifiy your plans to to fit your ammo.

By the way I took  my  6 inch diameter beer can mortar tube and opened it up to shoot  6 PDR ball

[irishman]

DD,     Thanks for refreshing my memory. Used to buy those in a bar for 25 cents. I go back to 2.605 divided by 39X40=2.67. This all started with a 5" X 10" 60 lb. blank; print looking for 2.625.  I will post pics.

     What diameter did you increase that 6" od to for the 6 PDR?

                                                     Michael

     

[Double D]

Bore is  3.67.  My Ball Mould is 3.58 diameter.  Cast Zinc ball go 6 lbs





I think your tube may be a wee bit skinny for a 6 PDr. 

You could band it.

[irishman]

wee bit skinny? I can see it blow to bits just thinking about it. I will go to Camp Grayling this year to expose myself to the big stuff.

I'm in the middle of cutting my first beer can bore. By far the largest yet and has consumed alot of my attention. Started with 5" dia. X 10" blank which is 60 pounds. I wish I had time to do more of these.

[Double D]

I think you will find that if you get the look right and can keep cost factors down you will sell quite a few. Pop Can Mortars have this "appeal"  for a first cannon.