.50 Bore BP Charge

[walter t]

Hi All,
New here, great site, just made my first cannons , an 8" bronze ships cannon with a .50 bore made from 1 1/2" bronze boat shafting,  also a golf ball mortar , I am not sure of what size charge to use, I have some ffg and fffg powder, some recomendations would be great. The mortar is made from a peice of 3" aluminum round bar, bored 1.70"  for golf balls, wall thickness  is .65" and at the powder chamber it is 1", lenght of bore is about 4", is this safe to shoot?
Walter t

[Cat Whisperer]

Walter -

WELCOME to the board.  We'd love to see some pictures of your cannons and of them firing!

Let me give you a partial answer - start with Fg and FFg to keep your pressures low. 

What does the inside of the bore look like at the bottom - is it hemispherical or flat bottomed or does it have a powder chamber?

I've never seen anyone do a mortar  in aluminum.  That alone should tell you something.  Pressure shooting golf balls is, however, low.  It might be ok, might not.  I'd measure the OD very carefully and accurately for baseline data.  You might try about 30grains of FFg under an unpatched golf ball.  I would make sure that you have something substantial between you and it.  Then keep track of any swelling (use a dial caliper to measure it).  That might work, or it might just come unglued unannounced.

Brass is a bit stronger.

[walter t]

Hi Cat Whisperer,
Both the cannon and mortar have powder chambers, the cannon chamber is about  3/8" dia. 1/2" deep and is stepped with a fairly sharp transition from the 1/2"bore , I cut the bore with a 1/2" bit then went down to 3/8" for the powder chamber, I shot it once useing slightly less than 3/4" teaspoon of ffg and some toilet paper wadding packed a bit and let out a nice crack and jumped backa bout 6" or so. The mortar was done the same way, bored .50 dia. for 2.6" then bored to 1.7" dia. to a depth of 2" then 1" for 1/4" leaving a powder chamber 1/2" deep for about .4" and stepping up to 1"for1/4". The chamber on the mortar will hold about the same as the cannon, about 3/4 of teaspoon of powder . About how much powder would 3/4 of teaspoon be? I will post up some pics soon.
Walter t

[Artilleryman]

Walter, you need to get a scale to weigh your powder.  I am rather hesitant about using aluminum for any kind of barrel that is going to be fired.  As to a powder charge for the cannon, I don't shoot cannons that are .50 caliber, but I do shoot a Smith carbine with 25 grains of fffg which is plenty for target shooting out to 100 yards.  I would start low and work up a load.  Someone on this board with experience using .50 caliber cannons will offer a load.  Just remember that you can't make a small gun perform like a big one.  Since you are just getting into this be sure to ask questions about anything that you are not sure about.  The people on this board are more than happy to offer advice.

[Cat Whisperer]

Walter -  Listen VERY CAREFULLY to what Norm says.

Experience is something that I equate to WISDOM, he has it.

[GGaskill]

The main problem with aluminum is that is never reaches a plateau in repetitive stress (fatigue.)  No matter how overbuilt, it will eventually fail.  Steel does not have this problem, nor apparently does brass/bronze.  As long as you stick to golf balls, I would expect it will take a long time to reach failure.  But it will happen if you shoot it enough.

[walter t]

Hi All,
Thanks for the replies. The aluminum motar I made will sit on the shelf, I do not want a grenade! I will get some powder measures and start to work up a load for my .50 cal cannon . I live in a  fishing community in the Canadian Maritimes and there is 5 + machine shops  in this small town with all kinds of ends of shafting, I will get an end of 4" s.s. and make another golf ball launcher,,,
Walter t

[Rickk]

With the 3/8 diameter by 1/2 inch deep chamber in your fairly thick walled 50 cal cannon I don't think it would actually be possible to overcharge it with any amount of any type of powder that will fit in the chamber.

What you have is pretty much in the same class as a thick walled black powder pistol, and there is a sub-chamber to reduce the chamber size even further.

I would base your charge on recoil more than anything else. If you are shooting 50 caliber balls the recoil will move the gun back quite a bit. You want to launch the ball, not the gun.

You can certainly start with 2F, but 3F is not out of the question either if 2F won't get the velocity you want.

You can try patching the ball as well, although loading a patched ball in a smoothbore is harder than in a rifled barrel. Try a looser fit patch/ ball combo first. 490 molds are common. A 490 mold with a .010 patch will fit tight. If you can find a .480-485  mold that would maybe be a better choice. I don't know where you can get one... Maybe consider a thing as small as a .457 ball with a thick patch.

For a frame of reference, see
somehttp://www.traditionsfirearms.com/files/Cannon_manual.pdf
remember that their cannons are rifled, which gives the patch someplace to go. The recommend 20 grains 2F as a max charge for their 50 cal, although they do mention without recommendation as to quantity that 3F can be used in their smaller guns (50 cal is their smallest gun).

Lacking a subchamber, their guns have much thinner walls than yours.

Also, look here :
http://www.traditionsfirearms.com/eshop/products/TRADITIONS%20SIDELOCK%20BOOK1.pdf
for BP Pistol loading data. If you call your gun a .32 roughly the sub-chamber size) the recommend 20 grains 3F max.

My CVA 45 caliber cannon recoils so much with the max charge they recommended (I forget offhand what that was) that I cut way back to keep the gun from leaving my yard.

Start low, and base things on maintaining reasonable recoil mostly. Keep the charge under what the above references (for thinner walled guns actually) recommend and you will be way safe.