What we may be running into with the plug gauges Hamilton found since they were in a proof house the gauge marked on the plug was for the bullet to be used for proofing a barrel the plug fit. This is what we run into when knowledge is lost. I would not be surprised if there is an explanation in some old book someplace in the British Isles but finding it might be a problem. Or they simply used that plug gauge to determine the proof load. Unless there is a written explanation found I don't see how to resolve this. Or they never wrote it down but simple passed it on the apprentices as on of the "secrets" at this date who knows.
A round ball of pure lead can have its weight accurately calculated. So 16 to the pound would be the same weight and so the same diameter anytime it was measured/weighed.
.682 would be a just a little bigger than 15 gauge at 478 gr according to Beartooth Bullets RB weight calculator. Which matches all my actual measurement/weighing tests. But a 682 bore will shoot a ball in the .672-662 range or perhaps smaller if its a smooth bore with "issue" ammunition.
.662 is 437 gr on my scale, so its a "#16" ball. Beartooth agrees.
Usually rifles shoot a ball about one gauge smaller than the bore in 62-69 calibers for a fairly tight fit. Forsythe describes using a #15 ball in his 14 gauge rifle with a substantial patch. Some modern target shooters use a bore sized ball or even slightly larger.
In a 54 I shoot a .535 which is 30.3 to the pound. The bore being 29.5 to the pound according to Beartooth. A 495 in a 50 cal is also one gauge smaller 37.2 and 38.2. I use a heavy patch in both calibers.
Back in the day SB fits were looser since they did not keep the bores very uniform. Today using a ball within 1-2 gauges of the bore requires a thin patch. With the same patch used with a 50 caliber rifle a 50 smooth will load OK with a .480 the 480 is a 41.9 gauge
Rifles came with their own moulds unless military issue like the 1803.
The military musket was a holder for a bayonet as much as a firearm until well into the 19th c.
The French did some experimentation with the musket and in the early 19th increased the ball size to improve accuracy.
But I don't remember the ball sizes and the French were metric anyway.
This is detailed in "Firearms of the American West 1803-1865" IIRC.
So far as bore sizes go there was little in the way of tight controls of bore sizes until the advent of Smokeless powder breechloaders.
It is not uncommon to find 45-70 rifles from the 1870s-80s or even later with groove sizes in excess of .460. In fact .464 is pretty common. Since Sharps 45 calibers had a "nominal" bore size of .451 when we see most of the rifles over .455 and often much over that we realize that it was not that important. And this applies to the target models as well.
Given this we can understand how the bore sizes varied in the 100+ years before in the late 18th c. For this reason chamber dimensions and large bore sizes make it impossible to shoot accurately with smokeless powder or even difficult with BP unless the shooter understands how to make it all work.
So we have 18th c muskets that were often little more accurate than a wrist rocket, if that good, due to being what Hanger called "ill bored". With the issue loading hitting a man at 100 yards was iffy at 200 according the Hanger, one might as well fire at the moon. I would dig up the exact quote but its not worth it.
Dan
Dan,
Thank you for your thoughts and the time it took to type that out.
When you talk about a ball size for a rifle being One or Two Calibers less than bore size, do you mean .01" or .02" smaller than the stated bore size or do you mean .005" and .010" less than bore size? I apologize as I did not quite follow what you meant.
18th century British and French Military Muskets were loaded with paper cartridges and the paper was turned into wadding as I'm sure you know. For those who may not know, the tail of the paper cartridge was bitten off and a little powder poured into the pan. Then the rest of the cartridge was rammed down the bore. However, what we sometimes forget was the ball was also wrapped in the paper, so in effect it was an early use of a “paper patched ball.”
I am not sure if there was (and don’t think so) a standard thickness of the linen paper they used to wrap the cartridges and especially the ball. Linen Paper thickness probably ran .005” to .007” or more. The size of the patterns of paper used to make the cartridges, that have come down to us, suggest that each ball would have had about two thicknesses of paper all the way around the ball diameter. This means an added .010” to .014” of paper on each side of the ball or a total thickness of .020” to .028” that the “windage” or diameter of the bore was reduced. IOW, if the bore size was an actual .750”, then the paper around the ball reduced the bore size for the ball to .730” down to .722” or so. From the Archeological record, original British Musket balls run from a bare minimum of .670” to .690” with more of them tending towards the larger size. If we take the larger size of .690” and wrapped it in the paper as mentioned, the size of the paper patched ball ran .710” to .718” in a minimum .750” bore. (If the linen paper was thicker than these minimum sizes, it would even more “fill up” the space of the bore for the paper patched ball.) That .040” to .032” extra space was left so the Soldier could easily load the paper cartridges even after the bore became fouled with powder residue from firing many shots. It’s possible the Muskets shot more accurately as the powder fouling built up from firing more catridges and reduced the open space (or windage) around the paper patched ball.
There is more “windage” or open bore size around the paper patched balls when the bores run .760” to .780” as they seem to have been generally made. That leaves anywhere from .032” open space to as much as .060” open space in the larger bore size with the thinner size paper. I’m not sure a .780” bore size was considered “ill bored,” but I at least suspect those that ran .780” to .800” were considered “ill bored” and would have been far less accurate with the “Issued” cartridge paper wrapped ball.
If the balls used in Brown Besses actually better fit the bore size and a proper sized greased patch is used, they shoot one heck of a lot more accurately than what was capable with the original .69 caliber ball and paper wrapping. The bore size on my old reproduction Brown Bess Carbine was .753” and with a .735” ball and .020” greased patch, it would split the ball on the axe all day long at 25 yards IF I did my part in the Offhand. It would also take out a 1 Gallon Plastic Milk jug at least 9 out of 10 times, as long as I did my part at 100 yards from the Offhand. That’s well within the torso of a human being at that range. (I was in much better shape then in my 20’s and my eyeballs had not turned way off yet. Grin.) So Military Muskets then probably would have been significantly more accurate in the 18th century had the paper patched ball better fit the bore size. Good thing for we Americans that they did not. Grin.
Gus