How to figure ball diameter for your guns bore

[M. De Land]

Circa 1860's- 1880's when Brockway was active bullets were often called balls, a hold over from the round ball days. The target rifles he made would have used picket or sugar loaf bullets, as pictured above. Later parallel sided bullets used a two piece construction with a hard lead nose and soft lead base. I wonder if the patch referred to was a paper patch?

The trouble with what your saying is, with Roberts book in front of me page 417 ,the section heading is " CORRECT FIT OF ROUND BALLS " !

 

[Dusty_Traveler]

I have found that I like mine ~.013" under.

 

[Jim in Wisconsin]

There are a few editions to this book, mine doesn't even have 417 pages in it. I do have the section on called "correct fit of round balls" and it definitely says "minus" for patches. In the next paragraph he talks about picket or sugar loaf bullets and says the same rule is used, and also for paper wraps. Always minus, not plus. This is Brockway recommendations, and it's on page 267 of my old crusty edition with the binding falling off.

 

[M. De Land]

I have found that I like mine ~.013" und

There are a few editions to this book, mine doesn't even have 417 pages in it. I do have the section on called "correct fit of round balls" and it definitely says "minus" for patches. In the next paragraph he talks about picket or sugar loaf bullets and says the same rule is used, and also for paper wraps. Always minus, not plus. This is Brockway recommendations, and it's on page 267 of my old crusty edition with the binding falling off.

It seems to me Jim that it has to be bore plus patch thickness or there is nothing to fill the grooves against gas blow by and I know for a fact the patch is supposed in engrave the lead ball in the groove as well as on top the lands.
Remember most of these linen patch rifles had each groove cut up to approximately .010- .012 which means the patch needs to block off bore diameter plus .024 for both sides of groove diameter.

 

[Ed C.]

It seems to me Jim that it has to be bore plus patch thickness or there is nothing to fill the grooves against gas blow by and I know for a fact the patch is supposed in engrave the lead ball in the groove as well as on top the lands.
Remember most of these linen patch rifles had each groove cut up to approximately .010- .012 which means the patch needs to block off bore diameter plus .024 for both sides of groove diameter.

Again, you are saying the ball diameter is going to be larger than the bore diameter? Plus a patch? Good luck pounding that down the barrel! Could you post the exact text from the book?

 

[M. De Land]

Again, you are saying the ball diameter is going to be larger than the bore diameter? Plus a patch? Good luck pounding that down the barrel! Could you post the exact text from the book?

I'll see if I can get my camera to focus on the page and then I'm going out in the shop and plug gauge the bore in my .45 cal match rifle. I know I use a .445 ball diameter and a .018 shirt felt patch I cut myself. So this should give us good info on if the formula is correct or not.

 

[Ed C.]

I'll see if I can get my camera to focus on the page and then I'm going out in the shop and plug gauge the bore in my .45 cal match rifle. I know I use a .445 ball diameter and a .018 shirt felt patch I cut myself. So this should give us good info on if the formula is correct or not.

That seems right. The ball is still .005" smaller than a true .45 cal. bore. The patch will really squeeze down on the lands and still fill the groves. About the same as using a .495 ball in a .50 cal. Pretty tight, but doable.

 

[necchi]

Ned Roberts has been dead for 75yrs. And that was after he wrote the book.
The simplest way to explain to you is the technological advancements of our barrel alloys today, the powders we use and even the fabric we have, has been HUGE since those times, there simply isn't a way to replicate them with the "off the shelf" products we have available today.
Trying too replicate/produce the same results of his shared knowledge in today's world would require a full retro refit.
The fact of the matter is, his book is an enjoyable read of historical knowledge. A point to ponder of day's gone past.
It's not applicable today.

To be honest the only works of Mr. Roberts I have ever admired is his wildcat 1/4 bore cartridge gun, the 257 Roberts,, I've always wanted one,, but even those are lost to history,

 

[M. De Land]

I'll see if I can get my camera to focus on the page and then I'm going out in the shop and plug gauge the bore in my .45 cal match rifle. I know I use a .445 ball diameter and a .018 shirt felt patch I cut myself. So this should give us good info on if the formula is correct or not.

That seems right. The ball is still .005" smaller than a true .45 cal. bore. The patch will really squeeze down on the lands and still fill the groves. About the same as using a .495 ball in a .50 cal. Pretty tight, but doable.

Well Ed, I can't make the formula work either, wither I add the patch thickness or subtract it. My bore measures a very snug .451 with a machine shop plug gauge and the the patch material mic's as I remember at .018 so .451 plus .018 means I need a ball diameter of .469 by that information and if I subtract the patch width I need a ball of .433. My .445 balls with the .018 patch material is a very snug load and with 65grains of 3F the most accurate I have yet tried and as you surmised there is no way to get a ball of .469 loaded down that bore with an .018 patch without a jack hammer.
Subtracting .018 from the bore diameter for a ball of .433 diameter would never seal off the grooves. Something is haywire either way with this information.!
Soon as my camera battery recharges I'll try to get page 417 to focus in a shot.
Tomorrow I'll make a Cerosafe slug, mic the groove diameter and see if that may shed some light.

 

[Dusty_Traveler]

I would also like to know if -edit- Brockway was using a short starter or not.

As a personal, traveling light preference of mine, I don’t carry/use a short starter very much. I know there are examples of early short starters, but they were not widely used.

I find a ball/patch combo that is tight enough that I can start with my thumbs stacked on it, or by a little wack from the heel of my hand. This has worked great for me as far as ease of loading after continued firing, and has lessened up one more piece of kit to carry. I will say that most of the time I use a felt wad under the patched ball. I mainly use these for a “scrubber” to help keep the fouling down, but this also works somewhat as a gas seal. This helps with the undersize ball. A handful of wads is lighter than a short starter.

I don’t punch a lot of paper, but my 80 yard plate rings consistently. It is about half the size of the vital area of a deer.

For me, using a .013 under ball gives me 3 different sizes of readily available commercial patching material to get the fit I want, and where it shoots the best within said parameters. The rifle and I work out the rest of the details.

 

[Jim in Wisconsin]

If you use the guideline of bore diameter minus the thickness of the patch, you still have an interference of one thickness because the patch is wrapped around the ball. That adds two thicknesses of material to the diameter.
In my 44 rifle, the bore is .444 and the patch (pillow ticking I think) is .015 -greased with mink oil. I use Hornady .433 balls and that is pretty tight.
If you were to add the thickness, that would mean a ball diameter of .459 which would be impossible.
I think M. DeLand and I are saying the same thing, just in different ways.
Dusty - that wasn't Ned Roberts's formula, is was N.S. Brockway's. I don't know who that guy was though.

 

[Dusty_Traveler]

Thanks Jim. Fixed. Pre coffee issues.

 

[Grenadier1758]

Well Ed, I can't make the formula work either, wither I add the patch thickness or subtract it. My bore measures a very snug .451 with a machine shop plug gauge and the the patch material mic's as I remember at .018 so .451 plus .018 means I need a ball diameter of .469 by that information and if I subtract the patch width I need a ball of .433. My .445 balls with the .018 patch material is a very snug load and with 65grains of 3F the most accurate I have yet tried and as you surmised there is no way to get a ball of .469 loaded down that bore with an .018 patch without a jack hammer.
Subtracting .018 from the bore diameter for a ball of .433 diameter would never seal off the grooves. Something is haywire either way with this information.!
Soon as my camera battery recharges I'll try to get page 417 to focus in a shot.
Tomorrow I'll make a Cerosafe slug, mic the groove diameter and see if that may shed some light.

Let's take that 0.451" bore and look at fitting that 0.445" ball. We have (0.451-0.445) 0.006"/2 or 0.003" of windage between the ball and the lands. If the patch material is 0.012" compressed or 0.018" uncompressed. we have two thicknesses of patching that go between the ball and the bottom of the groove or 0.445 + 0.018*2 (Ball and patch of 0.481" before compression into the barrel). The patch material is going to displace some of the soft lead ball as the patch is compressed in the 0.003" between the lands and the ball. If the grooves are 0.010" deep, the 0.018" patch is getting compressed to 0.013". That's enough compression to lightly impress the patch groove location onto the ball and with patch lubrication effectively seal the barrel. Well, never perfectly, but adequately. Yes, it takes a good sharp rap with the short starter to get the ball and patch into the muzzle. Once the lead ball is impressed into the patch at the lands and in the groove, the ramrod can push the ball and patch to the breech.

 

[Rich44]

You need a book to tell you what size ball to use?

 

[Grenadier1758]

Shouldn't need anything other than a digital Vernier caliper.

 

[Spillikins]

For example if your bore measures .400 and the patch thickness is .009 then your ball size should be .409 for that thickness of cloth patch.

This is just silly. What if you wanted to use a .020 patch? Are you saying that the ball should then be .420?
Anyone can see that this is simply an error on your part or in your edition of the book, and it should be minus, not plus. It's so bleeding obvious.
Just listen to Jim in Wisconsin.

 

[M. De Land]

Let's take that 0.451" bore and look at fitting that 0.445" ball. We have (0.451-0.445) 0.006"/2 or 0.003" of windage between the ball and the lands. If the patch material is 0.012" compressed or 0.018" uncompressed. we have two thicknesses of patching that go between the ball and the bottom of the groove or 0.445 + 0.018*2 (Ball and patch of 0.481" before compression into the barrel). The patch material is going to displace some of the soft lead ball as the patch is compressed in the 0.003" between the lands and the ball. If the grooves are 0.010" deep, the 0.018" patch is getting compressed to 0.013". That's enough compression to lightly impress the patch groove location onto the ball and with patch lubrication effectively seal the barrel. Well, never perfectly, but adequately. Yes, it takes a good sharp rap with the short starter to get the ball and patch into the muzzle. Once the lead ball is impressed into the patch at the lands and in the groove, the ramrod can push the ball and patch to the breech.

Yes, this is what is happening and works, the book formula isn't working at all for my components and diameters using the boar diameter hence the investigation plugging in the groove diameter to figure out what Brockway was proclaiming.

 

[M. De Land]

This is just silly. What if you wanted to use a .020 patch? Are you saying that the ball should then be .420?
Anyone can see that this is simply an error on your part or in your edition of the book, and it should be minus, not plus. It's so bleeding obvious.
Just listen to Jim in Wisconsin.

The minus patach thickness doesn't work either with my dimensions of bore, ball and patch thickness. What does work is a .445 ball,.018 patch with spit or windshield wash lube and 65 grains of Goex 3F. One simply cannot get to what is working using Brockways formula as written.

 

[tenngun]

You are overthinking this (non) issue. Unless you are working with an old original with a strange bore size you won't have much looking to do to find the right ball size. You mentioned .50 cal. With today's modern barrels a .490" or .495" ball and proper patch will work perfectly. To find yer ball/patch combo all you need to do is try both sizes and several different patch materials. That ain't so bad as the name of the game is shooting and it requires shooting to dial in yer new smokepole.

Using open iron sights I doubt most of us can shoot as well as the best tge gun could do. The difference our average shooter will get from the most perfect load and a load that’s handy to load at the range or field may be a little different. However, average human eyes, real life variations in temp and wind and lighting will not effect the down range results

 

[M. De Land]

I'll see if I can get my camera to focus on the page and then I'm going out in the shop and plug gauge the bore in my .45 cal match rifle. I know I use a .445 ball diameter and a .018 shirt felt patch I cut myself. So this should give us good info on if the formula is correct or not.

Here is the page out of the hard cover addition of Roberts Book Ed.
I made a Cerosafe cast of my match barrels bore and the groove diameter mics .478. The Bore is .451 so each groove is .0135 deep for a total cross groove depth of .027. If I take my .445 ball and add full patch thickness on both sides of the ball in relation to the groove (.018 x 2 = .036). Ball at .445+ both sides of patch .036 I get to .481 and my groove diameter mic's .478.
Ball plus double patch thickness gets me to .481 using the groove diameter as the base measurement I get within .003 of a match so with a .003 patch compression into the ball the grooves are sealed and the ball fully engraved. I know the ball is patch engraved with this component combination because I have pulled some I dry balled and checked.
So the re- calibrated formula for ball diameter seems to work out using groove diameter minus double patch thickness and figuring .003 of patch engrave-meant into the ball. This is a snug fitting load that does not need to be pounded down but probaly 20-25 lbs of pressure using a solid steel 5/16s range rod with a down the muzzle bore protector and delivers accuracy with good patch performance.
I think that makes sense................ no ?
Note the crown and how sharp the land ends are after hundreds of rounds shot. This is because a down bore brass muzzle guide/protector is always used when loading or cleaning.
The polish ring on top is from patch knife rub.