Quarter scale howitzer bore questions

[john pike]

forgot to ask,

the plans i have for a 1/2 scale howitzer, has a 1inch powder chamber
and a 1.5 inch bore,

my 1/4 scale i've drilled out a 1/2 inch powder chamber,
and haven't drilled out the bore,

1-can i leave it as is and safely fire it?
 or is there too much combustion?


i have .54 wall thickness(around the stepped area of the powder chamber)
 wich is keeping to the scale of the 1/2 scale cannon of course scaled down by half. whew,,,hope you get that one.


johnp

[Double D]

my 1/4 scale i've drilled out a 1/2 inch powder chamber,
and haven't drilled out the bore,

i have .54 wall thickness(around the stepped area of the powder chamber)
 wich is keeping to the scale of the 1/2 scale cannon of course scaled down by half. whew,,,hope you get that one.

As long as the wall thickness around the breech is the same as the diameter of the breech or greater. you should be fine. You have a 1/2 inch powder chamber then the walls around the breech need to be  1/2 inch thick, minumum.  

It's the bore that is a little worrisome.  Using the measurements you have given I think your round stock is 1.58 inch diameter.  Following your  1/2 formula you are planning a  .75 inch bore.  That will leave you with .415 walls.

What are you going to use for charge and projectiles?

[john pike]

my 1/4 scale i've drilled out a 1/2 inch powder chamber,
and haven't drilled out the bore,

i have .54 wall thickness(around the stepped area of the powder chamber)
 wich is keeping to the scale of the 1/2 scale cannon of course scaled down by half. whew,,,hope you get that one.

As long as the wall thickness around the breech is the same as the diameter of the breech or greater. you should be fine. You have a 1/2 inch powder chamber then the walls around the breech need to be  1/2 inch thick, minumum.  

It's the bore that is a little worrisome.  Using the measurements you have given I think your round stock is 1.58 inch diameter.  Following your  1/2 formula you are planning a  .75 inch bore.  That will leave you with .415 walls.

What are you going to use for charge and projectiles?

the diamiter of the stepped area, (outside) around the powder chamber(breach?)
is 1.56
 minis the .50 bore = 1.06 div by 2 = .53 wall thickness around
the 1/2 powder chaber/ bore.

i have not  drilled out the bore, i was going to leave the whole tube/bore
1/2 inch,

no projectiles planned, just for noise.
would it be louder if i bored out the bore to 3/4 ?
that would be following the plans.

johnp

[GGaskill]

would it be louder if i bored out the bore to 3/4 ?

For a given powder charge, it would probably be louder with a 1/2" bore than a 3/4" bore (the pressure at muzzle will be higher due to less expansion in the bore.)  Although you might measure a marble and drill the bore for that on the remote chance you will decide you do want to shoot projectiles.

Try to find the smallest fuse you can and drill the vent for that so you don't lose pressure out the vent.

[GGaskill]

It's the bore that is a little worrisome. Using the measurements you have given I think your round stock is 1.58 inch diameter. Following your 1/2 formula you are planning a .75 inch bore. That will leave you with .415 walls.

Since John is making a mountain howitzer pattern, the barrel OD increases in front of the chamber to about 1.725", so the wall thickness there is about .488".  But the bore is acting like an expansion chamber (similar to a Coehorn) so that should be adequate.  Plus I think he is going to leave it .5" bore diameter anyway.

[john pike]

It's the bore that is a little worrisome. Using the measurements you have given I think your round stock is 1.58 inch diameter. Following your 1/2 formula you are planning a .75 inch bore. That will leave you with .415 walls.

Since John is making a mountain howitzer pattern, the barrel OD increases in front of the chamber to about 1.725", so the wall thickness there is about .488".  But the bore is acting like an expansion chamber (similar to a Coehorn) so that should be adequate.  Plus I think he is going to leave it .5" bore diameter anyway.

im at 1.75  diam in front of the chamber,
tapering down to 1.614 at the front.

im going to leave it at .50 bore. all the way through.

what size are 50cal balls?? to tight i bet.

johnp

[Cat Whisperer]

.50 cal moulds commonly come in 0.490" diameter.

[john pike]

.50 cal moulds commonly come in 0.490" diameter.

is there enough windage?

Also "G" thanks for the drawings/plans, this ones practice for the 1/2 scale,



johnp

[Terry C.]

Using the textbook 39/40 ratio, the ideal ball would be .4875" in diameter. Balls generally do not come in this size, you get either .485" or .490" diameter.

I shoot .490" balls in a .50 caliber bore (simply because I have a mold that size) and have found this minute disparity in windage to be of no consequence.

If this were a muzzleloading firearm loaded with tight-fitting patched balls the situation would be different.

[GGaskill]

Since you should be swabbing the bore after each shot (to prevent premature discharges), .490" will be fine.