Is this right?

[dittles]

 My powder scale says that 2oz = 875.0 grains of powder. The rules say don't go over 2oz of Fg for every inch of bore diameter. So lets say that my cannon barrel is 1 1/2 inches in diameter, then I could technically put 1,312.5 of Fg in her,,,right?   Not that I would do it! Right now I'm sticking with 300 grains of Fg, for golf balls, and boy do those babies fly!

[armorer77]

In this case your bore is the powder chamber . 1"  Ed

[Double D]

My powder scale says that 2oz = 875.0 grains of powder. The rules say don't go over 2oz of Fg for every inch of bore diameter. So lets say that my cannon barrel is 1 1/2 inches in diameter, then I could technically put 1,312.5 of Fg in her,,,right?   Not that I would do it! Right now I'm sticking with 300 grains of Fg, for golf balls, and boy do those babies fly!

Wrong,  for chambers under 2 inch use the graph found on Switliks book which we have posted by permission in our safe loads sticky.  Maximum safe load for a solid projectile in 1.5 inch is 500 grains.

[Cat Whisperer]

dittles --

Good that you asked.  Some of US have just winged it and 'gotten away with it'.  Not the smart way.
 

Overcharges can start cracks that don't fully develop until years later.
 

[Soot]

How do you calculate what size the powder chamber should be.
I about ready to bore my 1/6 scale 1841 8" siege howitzer.
The bore will be 1 1/16. Not sure about the chamber yet.

[dittles]

"1. Powder charges should not exceed 2 oz. of Fg or 3 oz. FFA or Cannon Grade Goex powder per inch of bore diameter." Quote from the sticky. Well then according to my scale 2oz= 875grains. (I had a feeling that "bore diameter' really meant powder chamber diameter and not bore of the barrel, could of made it a little more clearer for us green horns, ). So I guess what I'm getting at, is my powder scale wrong? And how many grains of B.P. is in 2oz?

[Cat Whisperer]

The general rule of thumb, that keeps   you safe (given the other 'ifs' are taken care of), is that the diameter of the powder chamber should be at most 1/3 of the diameter at that point.  Also that the amount of metal behind the chamber would be at least as thick.

[Soot]

The section over the chamber is 3". I know about the 1 caliber rule.
Using the load chart from the stickies, the max load should be about 180 gr.
What I'm getting at is, does it matter if there is an air space between the charge and the projo?
I was going to make the chamber 3/4" diameter, not sure about the depth.
I may also increase the bore to 1.25, but thats another $80.00 + in bits if I decide to do it.

[GGaskill]

What I'm getting at is, does it matter if there is an air space between the charge and the projo?

In thick walled guns such as these, it doesn't make much difference.

And how many grains of B.P. is in 2oz?

One pound is 7000 grains so one ounce equals 437.5 grains so 2 oz is 875 grains.

[Double D]

"1. Powder charges should not exceed 2 oz. of Fg or 3 oz. FFA or Cannon Grade Goex powder per inch of bore diameter." Quote from the sticky. Well then according to my scale 2oz= 875grains. (I had a feeling that "bore diameter' really meant powder chamber diameter and not bore of the barrel, could of made it a little more clearer for us green horns, ). So I guess what I'm getting at, is my powder scale wrong? And how many grains of B.P. is in 2oz?

The quote from the sticky is.....

Safe Loads
For guns under 2 inch use the chart below.
National Safety Rules and Procedures for Shooting Muzzleloading Artillery, as adapted by the American Artillery Association March 2000
1. Powder charges should not exceed 2 oz. of Fg or 3 oz. FFA or Cannon Grade Goex powder per inch of bore diameter. No excessive charges. Use black powder only. 
2. Prepare powder charges in advance using heavy duty aluminum foil. Baggies may be used inside the foil, taking care not to allow excess air in the baggies and removing excess plastic where unnecessary.

N-SSA National Rules for Cannons
10.8.1 CHARGES
Maximum powder charges for all cannon shall be limited to that amount permitted by the chart as published below in Table 10.1. Only commercially manufactured black powder of American standard Fg granulation (150,000 granules per pound/ or 220 granules per 10 gr. wt. (avdp.) sample), or a coarser granulation, may be used. Charges must be wrapped in a powder “bag” fabricated of at least one complete layer of heavy-duty aluminum foil.

Added a bit of emphasis so you would see the part you missed.

So then you look down and here is this:

Moderator note: For guns smaller than 2 inch THE MORE COMPLETE CANNONEER compiled Agreeably to the Regulations of the War Department as published in "Artillery Drill" by George Patten, 1861 and Containing Other Observations on Antique Cannon By M.C. Switlik with selected excerpts from other artillery manuals Appendix I has a load chart which is posted here by permission of the author.



To see a large view of this chart click on this link: http://www.fototime.com/90BD33C5013C58D/orig.jpg

This load chart is maximum load of a unpatched ball attached to a sabot.

 Addendum For mortars and howitzers the diameter of the powder chamber is the considered the bore diameter.

[Double D]

The 1841 8 inch had a 4.62 in diameter chamber.  So at 1/6 scale you bore should be 1.336 and your powder chamber .773.

1.0625 bore needs a .615 chamber

[armorer77]

Since this started about one of my designs , I would like to mention that the wall around the 1" chamber is 1.5" in this case .

When in doubt , go with overkill . Ed

[armorer77]

I have to issue a correction . That is 1" chamber with 1.25" walls .  Ed

[keith44]

Just as a matter of varification, my kit cannon from Traditions came with load instructions that include a .69 cal lead roundball and a powder charge range of 45 gr of FF minimum to 85 gr of FF maximum.  Looking at the chart you could read it to allow 90 grains.  Very close to the manufacturers recommendation

[Cat Whisperer]

...
When in doubt , go with overkill . Ed

 

[dittles]

O.K. guys, I got a confirmation that 2 oz=875 grains but the graph on the sticky says 1oz= 480 grains. So at 480 grains for 1 oz x 2 =960 grains per 2oz. 960 grains is in 2oz according to the graph in the sticky. There is 875 grains per 2oz according to my scale and  GGaskill, thus there is a 85 grain discrepancy between the two. So who is right, the graph or my scale?  P.S. ,Ed I like the way you think!

[keith44]

What I'm getting at is, does it matter if there is an air space between the charge and the projo?

In thick walled guns such as these, it doesn't make much difference.

And how many grains of B.P. is in 2oz?

One pound is 7000 grains so one ounce equals 437.5 grains so 2 oz is 875 grains.

 

[Double D]

Yes the annotation is wrong the graph is not.  Use the graph and don't think about it.

480 grains in a Troy ounce. 437.5 grains in a avoirdupois ounce.

The chart say says use avoirdupois.

Powder is always weighed in avoirdupois.

[dan610324]

another good rule of thumb is 0,15 - 0,2 gram powder per 1 mm bore (chamber) diameter

so a 50 cal bore cannon ( approximately 13 millimeter ) could use between 1,95 - 2,6 gram  ( 30 to 40 grains )

0,15 for cast bronze and 0,2 for turned steel barrels
1 gram is 15,43 grain

thats the maximum loads used by many german cannon clubs for cannons betweem 1/4" and 3/4" cal

[Cat Whisperer]

another good rule of thumb is 0,15 - 0,2 gram powder per 1 mm bore (chamber) diameter

so a 50 cal bore cannon ( approximately 13 millimeter ) could use between 1,95 - 2,6 gram  ( 30 to 40 grains )

0,15 for cast bronze and 0,2 for turned steel barrels
1 gram is 15,43 grain

thats the maximum loads used by many german cannon clubs for cannons betweem 1/4" and 3/4" cal

Cool.  We need to put that into the sticky!

Thanks, Dan.

[Double D]

another good rule of thumb is 0,15 - 0,2 gram powder per 1 mm bore (chamber) diameter

so a 50 cal bore cannon ( approximately 13 millimeter ) could use between 1,95 - 2,6 gram  ( 30 to 40 grains )

0,15 for cast bronze and 0,2 for turned steel barrels
1 gram is 15,43 grain

thats the maximum loads used by many german cannon clubs for cannons betweem 1/4" and 3/4" cal

Cool.  We need to put that into the sticky!

Thanks, Dan.

Don't quote it with out a source to link it to.  Dan do you have a link for us? Also that reference will have to be clearly  and loudly marked for metric or some one will be trying find grains with it.

[dan610324]

sorry dd , no idea where I read that
it was many years ago , but Im sure that Ive read it at more than one place

[PaulB]

Wrong,  for chambers under 2 inch use the graph found on Switliks book which we have posted by permission in our safe loads sticky.  Maximum safe load for a solid projectile in 1.5 inch is 500 grains.
[/quote]

One of the problems with the chart for those bores under 2" is the grey area between 1 1/2" and 2".
I have fired my 1 3/4" bore with Fox balls over 700gr of cannon grade and it seems light

[Double D]

What about it seems light?  The fact that it equals 700 grains  or is it that 2 oz per inch formula equals 1531 grains.

Or does 700 grains not perform properly.

There are two ways you can interpret that chart.

You extend the chart  with the last segment as a straight line  to 1.75 or you can extend the chart to 1750 grains and 2 inch and draw a line  from the ending segment to 2 inch/1750 grains.

Just extending the line to 1.75 inch gives you  a max load of 900 grains. 

If you connect the line segment with 2 inch/1750 grains you will come up with a maximum load of about 1110 grains for 1.75 in barrel. 

I think either one of those numbers would probably be safety to work with. 

At 2 oz.  per inch the max load would be 1531 grains. 

Remember these are max load numbers not goals to achieve.  You are at 700 grains now, work up incrementally towards  900 grains. I think you will see a dramatic difference. May not be good.


Once you get the performance you are looking for stop.  If performance improves  but still isn't quite there when you get to 900 go ahead and work towards the 1110.

I think once you get into that range unless you have a very heavy gun and are using some light projectiles you may see your equipment get damaged. 

Go slow and go for what works best not maximum.
 

[keith44]

One of the problems with the chart for those bores under 2" is the grey area between 1 1/2" and 2".
I have fired my 1 3/4" bore with Fox balls over 700gr of cannon grade and it seems light

[/quote]

...
There are two ways you can interpret that chart.
...
Remember these are max load numbers not goals to achieve.  You are at 700 grains now, work up incrementally towards  900 grains. I think you will see a dramatic difference. May not be good.
...
Once you get the performance you are looking for stop.  If performance improves  but still isn't quite there when you get to 900 go ahead and work towards the 1110.
...
Go slow and go for what works best not maximum.
 

Ok first off gray areas and multiple interpretations of what is a maximum load should have everyone on full alert.  This is where things can go very wrong very fast.  Maximum loads are NEVER to be exceeded and NOT ALL GUNS CAN BE LOADED TO MAXIMUM!!!  I say this as a reloader with 20+ years experience, every load manual will repeat a version of that warning. 

To work up to a maximum load (find the maximum your gun (ie cannon) will safely handle) with BP loads increase the charge by no more than 10 grains at a time, until you get within 20% of the max load.  (if 100 grains is max being within 20% is  80 grains or more) then if everything seems OK and safe to increase the charge increase by 5 grains at a time.  These are the standards for BP cartridges which usually only hold the max charges, but it is the safest way to work up a maximum load.

I will not pretend to know all the symptoms to watch for with cannons nearing max pressures, the most obvious would be excessive flash from the vent, and excessive recoil.  Without a brass casing from fixed ammo the other symptoms of high pressure in rifles just do not apply.

Keith

[RocklockI]

For what is is worth , Mike Tracy and I all shot my .50 bronze VOC gun with .25 grains ....It was plenty !

In my Dom Parott gun 1.750 "    700 grains is the load I used at Cut Bank the one . It hit 500 yards pretty good with a fox ball .

Gary

[PaulB]

Or does 700 grains not perform properly.

There are two ways you can interpret that chart.

You extend the chart  with the last segment as a straight line  to 1.75 or you can extend the chart to 1750 grains and 2 inch and draw a line  from the ending segment to 2 inch/1750 grains.

Just extending the line to 1.75 inch gives you  a max load of 900 grains. 

 

Remember these are max load numbers not goals to achieve.  You are at 700 grains now, work up incrementally towards  900 grains. I think you will see a dramatic difference. May not be good.

Relax fellas'
I have been working it up slowly, ( I started at 480gr fg) I was just stating that 700 gr of CG seems like a fairly light load. I have a 1.75" bore so there is a little too much windage. If I use the VP Sim it says that with that load I should be hitting 665fps and 2857psi max breech pressure. I find those numbers believable but the next time out I plan on putting my chronograph in harms way and verifying the velocity if possible.

I have no interest in approaching maximum loads, I'm looking for about 750 -800fps and a decent report. I shoot my 1.25" barrel mostly with 250gr fg and its plenty.

[keith44]

Ok Paul, velocities are a very good indicator especially since you know where you should be.

[PaulB]

In my Dom Parott gun 1.750 "    700 grains is the load I used at Cut Bank the one . It hit 500 yards pretty good with a fox ball .

Gary

Gary, I'm curious, was that 700gr of CG or FG, I've heard folks use(confuse) the two interchangably and they're not. It takes over 1100 grains of CG in a 1.75" gun to reach the same pressures as 700gr of FG. Unfortunately some gun shops will sell you FG as "cannon grade"

[keith44]

Found this it is the only mention on their website of cannon grade.

http://www.goexpowder.com/goex-black-powder.html

With F grade (aka 1F) being mentioned for use in cannon I can see why most shops would not even carry true cannon grade.