Bore diameter 2nd try

[Double D]

Lets try this again.

I am building a model cannon to shoot in club matches.

The club furnishes the lead round ball and powder.

The balls supplied are .455 diameter. I want to shoot this gun with a patch.

What diameter should I ream the bore?

[GGaskill]

Well, I would say ball diameter plus twice the compressed thickness of the patch.  Although using patches will mean you are shooting knuckleballs.  I would think you would like to get some reliable spin to the shot somehow.  Maybe patch on one side only?  Then your bore size should be ball dia plus one compressed patch thickness.

[Cpt Ed]

I agree with George,

Use .010 thickness pre-lubed patches with the .455 ball and ream the bore .475

You will have much better accuracy with a patched ball than without the patch.

I use a pre-lubed patch with my 1.5” half scale Parrott and now I am able to place 75% of the rounds on the target.
Prior to using the patch I was lucky to have 10% hits on the 6’ diameter target out at 200 meters.

[Rickk]

How hard do you want to hammer the ball down the bore?

Is it rifled or smooth bore?

I have a 50 cal hawkins style target rifle I put together myself. It will group 1 inch groups at 100 yards all day.

I shoot a .495 ball with a .010 patch. I need mallet to get the ball started, and a serious stainless steel rod (with bore protector) to ram it home.

Tighter is better as long as you can get the ball down the bore. If it is rifled, I would not go more than .010 over ball size.

If it is smooth bore, you will have to go looser. 0.475 does sound reasonable for a smooth bore.

You can always play with patches to make it tighter. I would try some .010's and some .015 patches first. If you can get the .015's to fit you will more than likely be grouping tighter. Use a 7/16 hardwood dowel for a ramrod and dont be surprised if a wooden or rubber mallet comes in handy. If the barrel is a bit on the long side you will want to have a short "starter" ramrod to get the ball started. The shorter one will flex less when you are trying to get the all started. Once it is started it will go in more easily so you can switch to the longer rod at that point.

Fitting the ramrod with a wooden block or hardwood ball on the end will give you a better surface to hammer on with the mallet.

I tried some of the fancier patch lubes but always came back to Crisco. It works well and is really cheap. It will go rancid if stored for months in warm weather, so don't prelub a year's worth of patches on a rainy day.

Rick

[Cat Whisperer]

It would make an interesting experiment to ream several short sections to a sequence of sizes - to teste the feel of different patches on each size.

I've tried patched ball only once or twice, in a 50 cal percussion rifle - with less than match-winning results (as expected).  I do remember some of the folks using a variety of materials for patches - from cotton sheets to pillow ticking.

[guardsgunner]

DD,
   There are alot of smooth bore shooters who do very well by running the ball within a couple of thousands of the bore and using a hard greased ball.(Beeswax and oil)ect.So you might try .457 and avoid all the patching. If it looks like it may do better patched, ream it larger.

[Rickk]

thanks for bringing that up guardsgunner...

with my .495 balls in my 50 cal, I use soft lead, not wheel weights or range scrap. The fairly pure lead is more willing to deform when I wap on the ball starter with a mallet.

If the provided balls are not near pure lead, you will not be able to push the fit as close as I do. Pure lead marks with a fingernail fairly easily, lead with tin and antimony in it doesn't mark as easily. Best is to compare against some known samples to get a feel for it... like some commercially produced cast handgun bullets for instance. They should be "hard" lead.

I use a Saeco bullet hardness tester to check alloys accurately.

Now that it is all coming back to me, there are so many variables that maybe the best thing to do is not worry too much about it and play with patch thickness.... the tighter the better untill it becomes too hard to start them.

[Double D]

I only get one shot at doing this as I have to have the barrel made for me.   I also shoot what balls are handed to me...made from range scrap, I believe.

Thanks guys for the ideas.

[claypipe]

  .455 Ball Size
+.030 Pillow Ticking .015 x 2
=.485

So I would say .480 - .485., depending on how tight a fit you want.

More Ugh=More Umph! This means the tighter the fit, the higher the chamber pressure and muzzle velocity.

Too much Ugh + Wrong Metal = Pipe Bomb. This means too tight of a fit combined with an improper metal and you get a face full of metal sharpnel.

CP

[Rickk]

Range scrap is going to be hard and not easily deformed. I would say add .020 to the ball thickness and go with that. Start with .010 patches. That should be an easy fit. You can try thicker ones to experiment with accuracy verses loadability.

[Cat Whisperer]

Have you measured the materials available for patching?  Either with calipers (micrometer) or by emperically testing?

[Cat Whisperer]

Another question - do you have access to measuring some of the other folk's cannons there?  (& compare measurements and their techniques to performance)

Or is the maneuver one of one-upsmanship?  To sneak in with "just a cannon" and win the poker game?

If you want, I can cut several 1 or 2" long rounds to a variety of bore diameters and ship them with a few more books.

[Double D]

Or is the maneuver one of one-upsmanship?  To sneak in with "just a cannon" and win the poker game?

Well, yes of course!!! Why else!!!