calibers and powder chambers ?? in mortars

[dan610324]

hope to get a lot of different explanations on my questions .

whats the real golf ball size ??
are they all exact same size ??

why are there so many different sizes for golf ball mortars ??
OK the difference ain't that big , but there are many different sizes mentioned here at the forum .
why doesn't all use the same size ??
please let me know how you have been thinking when you choose your caliber .


what size for the powder chamber ??
why that size ??

is the 1/40 th rule applyable here also ??
or is it any different rule here because of powder chamber and extremely short barrel ??


all those questions repeated , but this time for soda can mortars .

is there any similar rules for wall thickness on bronze mortars as the one caliber thickness in cannons ??
chamber wall and barrel wall .

should the bottom end of barrel still be radius shaped in an soda can mortar to get maximum strength ??
the can bottom aint shaped that way .

[Double D]

Check out the Reference sticky at the top of the board, you will find info about golf balls and cans there.

Different size mortars depend what mortar you are building.  If you replicate a Dictator it will be bigger than say a coehorn. 

I built my mortar chamber based on the maximum amount powder I wanted to use in my mortar. I weighed out the maximum amount of powder I wanted to use.  I put that in my adjustable powder measure and then measured the depth of the powder measure and made my powder chamber to the same dimensions

The windage rule applies. But 1/40 is not set in stone and is variable.  Windage is allows the gun to be loaded when the bore is fouled and helps control pressure.

References section has soda can meaurements.  But be forwarned those measurments are for US size soda cans.

CW will always warn you about stress riser and radiusing corners, its good advice. 

I regards to mortars the one caliber wall thickness rule applies to the wall of the powder chamber.

You can make a radiused ball seat if you wish.  I just use my compound to make a 30 degree angle.  That should work just fine for a can.

[JeffG]

I regards to mortars the one caliber wall thickness rule applies to the wall of the powder chamber.

I am far from an expert here, but a point that I am aware of: Chambered pieces are charged at chamber caliber, not bore caliber if you have a golf ball size bore and a 1 inch chamber, you measure your max powder  charges at chamber caliber.  Do I have that correct?

[Double D]

Yes, Jeff,  that is correct the powder chamber diameter in a mortar is used to determine powder charge.  And very good point!!!

[dan610324]

but when I start planning an golf ball or soda can mortar , what proportions should the powder chamber have ??

should it be 1/2" diameter and 4" deep or 1" diameter and 1" deep ??

how many grains is normal charge for golf ball and how many for soda ??

whats the best , small diameter and deep or larger and not so deep ??
if you got some recommendations please explain why you think so .

the tannenberg gonne was giving its best performance with meal powder , should that also be used in an chambered mortar ?? or cannon grade ??  or somewhere between ??

maybe better to have an very small diameter chamber and use meal powder .

please give me some ideas that we can have an discussion .

[jeeper1]

My golf ball mortar has a 1x1 powder chamber and is larger than I need. I use 200 grains of cannon grade or 100 grains of 3f BP. With either of those loads even an fluorescent orange painted ball disappears from sight still going up at over 250 yards. I estimate that I am getting about 400 yards out of it and that is more than enough for me.

[MikeR C]

Dan,
I had the same questions when I put my golf ball mortar together. Take a look at this post:

http://www.gboreloaded.com/forums/index.php/topic,127789.0.html

There seems to be a problem with large chambers producing unreliable ignition. I don't think this would be a problem if you want to put all your shots into orbit, but may present a problem if you want to be able to see the ball fly. I wanted to have a max range of about two hundred yards as that's about how far I can still see a ball.
I roughly followed DoubleD's dimensions and ended up with a mortar with a 1/2 dia chamber about 1" deep, not counting the 30 deg ball seat and just over a 2 caliber length bore, counting the ball seat. The vent puts the fuse into the very bottom of the chamber It holds approximately 50 grs of FFG and I figure the ball goes about 250 yards or so. I couldn't actually tell as I was shooting in a couple feet of snow and it made it real hard to find the balls. A half charge puts the ball at about a hundred yards making it easy to see the whole flight, doesn't help finding it in the snow however!
If you go back thru the old posts, and look for posts on the golf ball contest, you will find the results of each mortar design and drawings of the mortars that competed.

The best of luck with your new mortar,
MikeR C

[dan610324]

how about the idea to use meal powder in an tiny chamber , lets say 3/8 x 1 1/2 - 2 inch
what I can understand the meal powder have easier to explode instead of burning fast .
it seem to work well in the tannenberg gonne .

maybe the light weight of an golf ball makes it leave the barrel to soon,
 and all powder havent burnt out before the ball leave the barrel

thats why I am thinking of an small chamber and fast burning meal powder ,
preferably home made to have an even faster burning speed