Author Topic: Help a new guy determine proper charge weight (Read 721 times)

JRD · « **on:** March 19, 2006, 03:30:21 PM »

Hello to the board.
I've been bitten by the cannon bug. My dad has had a cannon barrel that a friend of his made for him about 30 years ago. He shot it occasionally, usually just as a noisemaker. I can remember a few times with him as a kid.

Well, I got the cannon bug now and have decided to shoot it some more because it is a blast.

Here's the specs. Turned (no doubt on a huge lathe) from a solid bar of "good steel" (according to my father, he can't remember the grade of steel that his friend said he used.) Well anyway, she's 4" OD with a 1.975" bore. 23" long OAL, with the bore being 18" deep. Flash hole is .187". She weighs 55 pounds. Not a copy of any historical cannon, probably determined by stock and tools on hand.

I found a suitable projectile that I scrounged from work. I got a handful of steel cylinders that are 1.920 in diameter and 2.3" long. They weigh about 1.25 pounds. They slide right down the bore with what seems to be just the right windage.

My dad and I shot it last weekend. I was burning Pyrdodex RS. Not real cannon fuel I know, but we have a bunch to burn and not much real BP. Rather burn the stuff on hand first. 200 grains (volume) with a newspaper wad packed down under the steel slug was pretty mild. 300 was a little louder and more potent. 400 grains was really potent.

We only fired about 8 shots total. After all this, what I'm asking, is: how do you determine a proper charge weight? With 1" thick walls, I probably have a decent safety factor. I don't feel much inclined to increase my charges anymore, but would like some advice.

Also, we were just propping the cannon up on the ground. I need to make a proper carriage for it. I've been looking at pictures on this forum and on the net. I haven't decided on a field or naval carriage. Scale wise, my gun looks most like a mountain howitzer, although it has no powder chamber, so would be a gun. (at least from what I've read.)

I'm looking forward to some advise from the board. We have a large gravel pit to shoot in, which is great for the cannon. I want to get educated to get the most from fun from the cannon.

Thanks,
Jason

Charcoal Burner · « **Reply #1 on:** March 19, 2006, 03:45:03 PM »

Does this barrel have a powder chamber?

JRD · « **Reply #2 on:** March 19, 2006, 03:51:48 PM »

No, it's almost a flat bottom.

Artilleryman · « **Reply #3 on:** March 19, 2006, 04:24:16 PM »

The N-SSA charge weight maximum for a 2 inch smooth bore is 4 ounces of 1Fg Goex with a maximum 16 ounce projectile. Your gun is slightly smaller in bore size. The guns used in the N-SSA have to be full scale and would weigh considerably more than 55 lbs. As with any load it is best to start out with light loads and work up. If you were to use 4 ounces of powder in your gun the recoil would be unacceptable. I would think that 1 ounce (437.5 grains) would be plenty, and I would work up to that. You have been using Pyrodex and I have no experience with it. It is supposed to be equal volume for volume with black powder, but that was for small arms use. Also there is no need for a wad when using a projectile.

With cannons the thing to remember is that you are not going to war with it. Also, forget what you have seen in the movies in terms the effects of cannon fire, they usually get it wrong.

Cat Whisperer · « **Reply #4 on:** March 19, 2006, 04:33:07 PM »

JRD -

Welcome to the board!

Is there much of a radius between the bottom of the bore and the inside walls of the bore - bigger radius means more strength (less of a stress riser than a sharp corner).

The newspaper under the projo will give you more velocity AND more pressure. The clearance (windage) on the sides of the projo help reduce the pressure.

How far forward of the base of the bore is the touch hole - at it or just in front - that too is a factor of strength.

Pyrodex takes a bit of pressure to get it to burn right. I burned up all I had years ago. Took a little black to get it going and then worked 'ok' but not really well in the mortars.

GGaskill · « **Reply #5 on:** March 19, 2006, 04:57:30 PM »

I expect you will find that an ounce (437 grains) of cannon grade BP is more powerful than 500 grains of Pyrodex in a cannon as you cannot reach the same pressure level in a cannon (with limited amounts of powder and shot) that you can in a rifle, and Pyrodex requires more pressure to burn successfully than blackpowder does.

Having said that, I second the notion of working up from a smaller charge as recommended above.

Cannonmaker · « **Reply #6 on:** March 19, 2006, 05:05:44 PM »

JRD,

From my experince with the bore size of 1.975, the tube weight or 55lbs, Projectial of 1.25lbs and a paper wad, 400 gr pyrodex RS should give concerderable recoil. This should have sent the tube flying backwards if the wad was packed tight.

Don't load heaver than you feel comfortable with and be conserative. Just enought powder to have fun, and no more and the cannon and us all will last and live longer.

When Lew, the promotor of the Big Reno Show told Nolan and myself we were crazy as we showed him the Cannons and Mortars and how they fired. He said we were crazy. We took this as a complement, although not to get out of hand.

As I say, THINK SAFTEY, ALWAYS SAFTEY FIRST.

Double D · « **Reply #7 on:** March 19, 2006, 05:53:49 PM »

I will echo what the others say and especially Artilleryman. Limit yourself to 1 oz. And work up to that. You walls over breech are a bit on the thin side. Don't not use a wad.

If you must use Pyrodex be sure and wash the bore and vent out with hot soapy water as soon as you are through shooting. That stuff is corrosive.

I must say I was impressed with your first post. You spent a lot of time in research and learned before you just dove in. Good Job and welcome to our little board

reddog · « **Reply #8 on:** March 19, 2006, 06:57:24 PM »

Good job guys these are the things i was wondering!!!

JRD · « **Reply #9 on:** March 20, 2006, 10:08:31 AM »

Thanks for the warm welcome. I have done a good bit or reading on cannons and do have a pretty strong background in shooting (both BP and modern stuff) and in gun design.

I think I've come to the right place. My goals are #1 Be Safe, and #2 Have Fun!

I am going to keep my loads conservative. First, I get more shots per pound of powder, and second you are correct, I am not taking the cannon to war. (At least if you don't count doing battle against sand piles at the gravel pit...)

My cannon bore is basically flat bottomed. Whatever radius there is, is probably defaulted to what was on the end of the machinists cutter. Also the touchhole is almost tangent to the bottom of the bore. I realize both are stress risers, but you take what you get and plan accordingly.

I am using a wad to affect a better bore seal. Pyrodex needs compression to burn efficiently and that's why I use it. Whenever I run out of Pyrodex, and have to switch to BP, I will work up a new load from the low side. (Pryodex with no ball and just a wad gives a just a whoosh with hardly any noise. No pressure is built beyond what's required to blow out the wad.)

Recoil with 400 grains was pretty substantial. We just had the cannon propped up and recoil blew all 55 pounds of cannon back several feet. Hence my decision that we need a carriage badly!

First get my cannon on wheels and shoot it more. Then, those pop can mortars you guys have look like a fun project. I've got my eyes open for a big piece of stock to start with....

Jason

Artilleryman · « **Reply #10 on:** March 20, 2006, 10:30:05 AM »

Jason, I like your goals. It reminds me of what I said to my crew twenty some years ago before our first national competition. I said to them first we follow all of the safety procedures, second we look professional, third we have fun, and if we place great.