How To Calculate Proper Ball Size

[Rokon]

Have an antique rifle with a bore size between 54 and 58 calibers and a coned muzzle.
Have been shooting a 54 caliber ball double patched with 0.020" linen. The load is accurate.
With 0.040" of patching on both sides of the ball, how would you calculate the approximate size of a proper fitted ball?

 

[Mulebrain]

I hold the rifle muzzle down, and try and slip a ball into it. If the ball won't push in, go the the next smallest size that will. Then proceed with different patching thickness for that ball. That is how I do it, others will chime in.

I just noticed your muzzle is coned, so then maybe two sizes smaller

 

[Grimord]

My method to determine ball size is to place a brass rod (1/2" diameter, 6" long for 50caliber & bigger) into the bore, then push a oversized lead slug into the bore about 2". Then invert the barrel (gun) and shake until the lead slug and brass rod comes out, then measure the land to land distance with a micrometer. Subtract 1/2 the thickness of your patch and you have a ball that fits the bore.

 

[Grenadier1758]

@Rokon, you have seen by now several recommendations for a calculation for a suggested ball size and patch thickness.

The unspoken truth is that all the calculations we suggest won't necessarily provide the accuracy you may want or the ease of loading. The proper ball size can only be determined in the final analysis by testing. Ball size is only one part of the proper load for your rifle. There is patch thickness that has a tight weave to resist cutting on the lands, good compressibility to fill the grooves to prevent gas cutting and engraving of the ball to the lands. You want the compatible patch lubricant to keep fouling soft between shots and not combine with the fouling to generate the black powder fouling crust. Then there is the amount of powder to match with the rate of twist and depth of grooves. Load development with your rifle and your components and lots of visits to the target range is ultimately the only way to determine the proper load for your rifle.

 

[mooman76]

What size ball are you using? Is it actually .540 or is it something else? They have .530 and .535 for 54. Its like Grenadier said though. You can do all the calculating you want but that just gives you and approximate until you try and see. Every gun is it's own and likes what it likes.

 

[Loyalist Dave]

Have been shooting a 54 caliber ball double patched with 0.020" linen. The load is accurate.

You could always just keep doing that, eh?

So a .530 ball (?) and .020 linen X2 = .040, wrapped around the ball is .530 + .080 would be .61. So with your linen patch material for a single patch you should look at a .570 ball, OR..., a .575 and also look for patching material that is .015. Hornady pre-COVID sold .570 round ball. Track sells both .570 and .575

This... ↑.... is of course a "paper exercise" and you won't know until you try them out.
Track of The Wolf Round Ball for Sale

LD

 

[Notchy Bob]

Have an antique rifle with a bore size between 54 and 58 calibers and a coned muzzle.
Have been shooting a 54 caliber ball double patched with 0.020" linen. The load is accurate.
With 0.040" of patching on both sides of the ball, how would you calculate the approximate size of a proper fitted ball?

@Rokon , you mentioned shooting a "54 caliber ball." Is that ball actually .540", or did you mean one of the balls marketed for .54 caliber rifles? You can get round balls in .520", .526", .527", .530", .535", and .540" from the various dealers online. If you are shooting an actual .540" ball with a .020" patch, you could try a .550" or .562" ball and a thinner patch. Track of the Wolf sells both.

I agree with the other fellows, though, in that it would be good to know the actual bore size, land to land. "Between 54 and 58 calibers " is a pretty big range. Among the myriad swaged and pre-cast balls on the market, you can find all of the sizes listed above, as well as .562", .570", .575", and .580".

The bottom line, though, is how well it shoots, and how much fun you are having with it. Some people will stop at nothing in the quest for pinpoint accuracy. Don Coble, a noted benchrest shooter in the fifties and early sixties, used a ball of bore size or even .001" over bore size? Walter Cline, author of The Muzzle-Loading Rifle, Then and Now, wrote that he achieved best accuracy with whatever sized ball could be just pushed down the bore by the weight of the ramrod alone, when the ball was bare or un-patched. That would probably mean right at bore diameter. For me, ease of loading is an important factor, and I'm willing to sacrifice some accuracy for easier loading. I tend to like a ball .015" or even up to. 020" under bore size, with a patch just thick enough to fill the grooves. There is at least one active thread on this forum discussing the use of .480" balls in .50 caliber rifles, and it turns out there are a number of us shooting balls well under bore size. Not that I'm recommending you do the same. As a matter of fact, if your current ball and patch combination is accurate and easy to load, there is no compelling reason to change.

It would be great if you could share your actual ball and bore sizes, though.

Best regards,

Notchy Bob

 

[mooman76]

Sure it isn't a 56 cal?

 

[SDSmlf]

I have found a ball diameter .010” under bore size, paired with a compressed patch thickness that gives a combination that fills the rifling within .001” or so can be loaded, ‘usually’ shoots pretty accurate and is a good place to start. Depth of rifling has to be considered, deeper rifling requiring a thicker patch.

 

[Rokon]

Thank you all for your insight and recommendations. Here's some additional data.

The .54 caliber ball I'm double patching with 0.020" linen has a diameter of 0.520 (Hornady). Yes, I could keep double patching since the accuracy is good but it is a pain-in-the-ass and uses up a lot of good linen.

Have some Cerrosafe casting metal on hand which could be used to cast an accurate slug of the bore. But the next question is, without removing the breech plug, what would be the best tooling to use to cast a slug from the muzzle and still be able to extract the slug from the bore. I was thinking something like a metal rod wrapped with friction tape to seal the grooves or would the brass rod trick work if I could seal off the bore with a wad of some kind while pouring Cerrosafe into the barrel.

Any help would be greatly appreciated

 

[Grenadier1758]

Take a relatively long 8-32 bolt about two inches longer than the cone in your barrel. Make a leather washer that is about groove diameter. With the bolt through the washer insert the bolt in the barrel so that about 1" is protruding. Pour your Cerrosafe into the barrel. When the Cerrosafe is solid, pull the bolt, washer and Cerrosafe from the barrel and you have your slug.

 

[mooman76]

Get some .530 RBs and try them and then 535 if you still feel you can go up another size. My guess is you can do .535 but that depends on your patch combo.

 

[Zonie]

Thank you all for your insight and recommendations. Here's some additional data.

The .54 caliber ball I'm double patching with 0.020" linen has a diameter of 0.520 (Hornady). Yes, I could keep double patching since the accuracy is good but it is a pain-in-the-ass and uses up a lot of good linen.

Have some Cerrosafe casting metal on hand which could be used to cast an accurate slug of the bore. But the next question is, without removing the breech plug, what would be the best tooling to use to cast a slug from the muzzle and still be able to extract the slug from the bore. I was thinking something like a metal rod wrapped with friction tape to seal the grooves or would the brass rod trick work if I could seal off the bore with a wad of some kind while pouring Cerrosafe into the barrel.

Any help would be greatly appreciated

Using Grenadier's method, pour only enough Cerrosafe in to the barrel to form a very short, full diameter cast plug. Don't pour a lot of material that would form a long slug that would be hard to remove. If you have it, a 1/2" diameter solid brass rod can also be dropped down the bore before inserting the leather washer.
Once the Cerrosafe is hard, if the threaded screw isn't enough to get the casting out of the barrel, a few good shakes can cause that brass rod to slam into the rearward side of the casting and drive it out of the barrel.
A word of caution about using Cerrosafe. The stuff has he unusual property of expanding once it is cool. This expansion takes a little time to develop but it can cause the casting to become stuck in the bore. The gist of this is, don't set the project aside figuring you will get the casting out later.

 

[Grimord]

That is why I suggested using a lead slug to drive into the barrel a short ways and using the brass rod as a slide hammer to remove the slug to measure. I had the unfortunate case of the Cerrosafe hardening in the bore, and had a heck of a time removing the slug.

 

[mooman76]

Me too and I never did get it out. Had to melt it out. I have heard that the cerrosafe if you leave it in too long expands. I'd rather us a lead slug now.

 

[user 34300]

I'd use the shanks of drill bits from my 115 piece index to find the go and no go sizes. I would then turn spuds on the lathe to get it perfect. One could turn a hardwood dowel in the drill press or electric drill and get close enough. To get the groove diameter slug the barrel and measure the slug. To determine if the bullet, patch barrel fit is good, use a strip of lubed patch material. Short start it, then pull it out by the cloth. Note how the fabric was impressed into the ball. Ideally there should be marks in the lands and grooves. That may be impossible with deep rifling.

Cerrosafe is great, I just don't have any.

 

[Billy Boy]

@Rokon, you have seen by now several recommendations for a calculation for a suggested ball size and patch thickness.

The unspoken truth is that all the calculations we suggest won't necessarily provide the accuracy you may want or the ease of loading. The proper ball size can only be determined in the final analysis by testing. Ball size is only one part of the proper load for your rifle. There is patch thickness that has a tight weave to resist cutting on the lands, good compressibility to fill the grooves to prevent gas cutting and engraving of the ball to the lands. You want the compatible patch lubricant to keep fouling soft between shots and not combine with the fouling to generate the black powder fouling crust. Then there is the amount of powder to match with the rate of twist and depth of grooves. Load development with your rifle and your components and lots of visits to the target range is ultimately the only way to determine the proper load for your rifle.

And therein lies the sport..

 

[French Colonial]

Cerrosafe melted and poured into the bore will shrink very slightly when it first cools and must be pulled IMMEDIATELY as it will expand again when completely cooled to the exact dimensions. This is what makes it so great for gunsmiths trying to find the exact cartridge dimensions for obsolete guns and proper bore diameters.
If you wait to long....you have a heck of a time getting back out of there...ask me how I know.

 

[Des52]

Agree with Mooman76, get some .350 round balls and try diferent patch sizes. Most .54s shoot well with these.

 

[French Colonial]

I am sure Des52 meant .530, shot some yesterday

My Jaeger likes .010 thick patch, the John Schreit likes .015, you never know until you experiment.