Max load for Golf Ball cannon

[Big Red 265]

 I am new to cannons and was looking for a little advice on max loads. I read the thread on loads but wanted to get some learned opinions as well. I should also note that I plan on usually keeping my loads relatively light but wish to know where my upper safe zone would be just in case I ever want to go the distance.
A machinist friend built me a golf ball cannon loosely to the specs I provided which were:
11" LONG
3" DIAMETER
1.695 BORE
8" CLEAR BORE DEPTH
2" DEEP X 1.250 POWDER POCKET
4140 STEEL
When he built it, he took a little artistic licence (which was great) and shaped it to look cannon like. This means that the breach end is a little bigger than 3” and tappers down to 3” in its thinnest spot. The powder pocket was machined separately and sweated in.
When surfing the web I find golf ball cannons that run max loads anywhere from 25 grains (Which seams pathetically small) to 500 grains (which seams scary big). A little help here would be great.
Thanks
PS   I have Goex FFg and Cannon

[brokenpole]

Big Red, the advice I believe you will get is togo buy the sticky at the top of the page that talks about safe loads and stick to it. There is a reason that iss a sticky on this site. It is for safety pure and simple. We do not need any more pipe bombs that kill the owner and all the spectators.


By your own post you said the cannon was built "loosely" to the design you provided. Was the cannon designed with the proper windage?




Be Safe!


bp

[Big Red 265]

 When I said loosely, I was referring to the profile of the cannon not the internals. All inside dimensions are within two thousandths.
 As far as windage, the bore is a (just barely) rolling fit for my golf balls. I used the specs for a Cannon Thunder produced golf ball cannon only my profile has given me a little more steel around the breech. I do have a concern about fouling making it to tight and if that’s the case, I will have to hone it out a little more.
 Avoiding a pipe bomb is precisely why I am on this forum (that and the fact that I find it interesting in general). When I read the chart, it is my take that 300grains is my max load because of the powder chamber in my cannon, 500 grains without it. This seems pretty high to me and I mostly want to see if others with experience would back up this max load.
I also read on this forum a post that said air space is not a significant concern. Is this true or do I still need to worry about it?
 

[Double D]

When I said loosely, I was referring to the profile of the cannon not the internals. All inside dimensions are within two thousandths.

Good enough.

As far as windage, the bore is a (just barely) rolling fit for my golf balls. I used the specs for a Cannon Thunder produced golf ball cannon only my profile has given me a little more steel around the breech. I do have a concern about fouling making it to tight and if that’s the case, I will have to hone it out a little more.

Windage is much too tight. Your bore will have to be absolutely spotlessly clean and yoru balls can not have any imperfection or debris on them or they will get stuck. If you move up to zinc or steel balls you could have problems.
 

Avoiding a pipe bomb is precisely why I am on this forum (that and the fact that I find it interesting in general). When I read the chart, it is my take that 300grains is my max load because of the powder chamber in my cannon, 500 grains without it. This seems pretty high to me and I mostly want to see if others with experience would back up this max load.

300 grains is a max load and for a cannon.  You will get no enjoyment from it at all.  Smoke, large consumption powder, ball never seen again, ho hum boring.   Reduce your powder charge with that chamber to about 30 grains. Fire a few shots. Adjust the powder charge by 5 grains at a time and keep adjusting until you get the ball out to about 100 yards.  Make a note of that charge. That is your optimum.  Keep increasing the charge until you reach point where the ball leaves to tube to fast to be seen or reaches 300grains.  That is your max charge.  For safety reason never shoot your mortar where or when you can not see the ball land on the ground

I also read on this forum a post that said air space is not a significant concern. Is this true or do I still need to worry about it?

The problem with air space is real, but very highly misunderstood, even by people who should know better-don't.   It is an old wives tale all airspace is bad, it is not an old wives tail that certain types  airspaces can damage certain guns. 

Your gun is not built to basic safety standards recommend for beginning cannon making- wall thickness over chamber be should equal to chamber diameter.   You have used 4140 which is the  type of steel used for making smokeless powder guns and gun barrels and yoru wall thick over chamber would be adequate for a smokeless powder cartridge gun.  I would think you are on safe ground using black powder in you gun. 

One thing we like to see around here is pictures....and some of us are not happy unless we see smoke and firre...so post them up!

And, welcome to our little group.

[Big Red 265]

Thanks for the great reply, it answers a lot of questions.

I never planned on firing steel or zinc balls, only golf balls. With this in mind, can I get away with my current bore diameter or should it be enlarged a little to accomodate a little fouling?

I was also curious as to what types of finishes are popular. I was toying with the idea of a shiny nickle plate (low maintenance) or parkerizing/black phosphate coating.

It may be awhile before I get my carriage built but I will try and get a pic or two up of what I have so far.

[Double D]

Thanks for the great reply, it answers a lot of questions.

I never planned on firing steel or zinc balls, only golf balls. With this in mind, can I get away with my current bore diameter or should it be enlarged a little to accommodate a little fouling?

I was also curious as to what types of finishes are popular. I was toying with the idea of a shiny nickle plate (low maintenance) or parkerizing/black phosphate coating.

It may be awhile before I get my carriage built but I will try and get a pic or two up of what I have so far.

Now while you are still building is the time to open the barrel up.   Once you shoot a zinc or steel ball you will never look back.

Mortars and cannons had black painted barrels.  You will find that a paint designed for high  temperatures like barbecue paint will work the best.  When your nickel starts flaking you will regret the nickel.  Never tried parkerizing a cannon, painting is so much easier, longer lasting, and easier touch up.

[Doc Brown.]

Hi Big Red.  Hi DD.  I just want to say this forum is awesome. I was about to make a golf ball mortar with a 1.695 bore and found out on here that it should be 1.72 This saved me a lot of pain and suffering because I was about 20 hours away from the point of no return.
 
I went with a pretty big powder chamber so that I can have a big boom and if I want still launch a golf ball.  I am worried about air space though. My powder chamber is 1" by 1.5 deep.  I have over 3 caliber wall thickness.

[Big Red 265]

Here are some pics

[GGaskill]

Trunnions are typically equal in diameter with the bore.  If you limit your projectiles to golf balls and lighter, you may not bend them, but otherwise they look too small.

[Double D]

Wit Trunnions that small rescind the suggestion to shoot steel or zinc.  I'd be reluctant to shot golf balls with that.

[Big Red 265]

I was using those for positioning and was going to tig weld some seamless tubing over them that was going to be cut to fit the profile of the barrel. This would take me out to one inch in diameter. After reading the posts I take it that that is still to small. I didn't realize how big they should actually be. I will have to see what I can do with some larger bar stock. The hard part is only having hand tools...should be interesting.