How did they decide on bullet diameter?

[mummac]

Why did Sam Colt make the .45 Colt .456 in. in diameter? Is there really that much of a difference with the six thousanths of an inch? Why is the .38 special .357 not just .35 or .36 or even .38? I wonder this about all cartridges really. The .40 S&W is actually .400 in.

 

[DrPsycho]

Probably in the early days it related to the size/diameter of the bullet but then as the years went by the marketting geniuses ruined it for all - as with all other industries.

 

[Jim March]

I can explain the 38/357 thing.

You've shot 22LRs before, right? If you're not intimately familiar with 'em, go grab one and look at it. (Or a 22short, they work the same way.)

The exposed part of the bullet is the part that is going to contact the barrel and is the SAME width as the shell. There's a "stub" at the rear of the bullet that is narrower and backs into the shell. But other than that, the 22LR *shell* is the same width as the bullet.

That's called a "heeled bullet". It's very archaic, it's how a lot of early metallic cartridges were built, such as the 44 Henry rimfire, and the earliest ancestor of the 38Spl. The only surviving "heeled ammo" is the 22LR/22Long/22Short family - the 22Magnum on the other hand is rimfire, but the shell is fatter and the projectile backs fully into it just like everything else.

So anyways, those really early 38s were really 38cal at the bullet, 38cal in the barrel and 38cal wide at the shell.

Heeled bullets were mostly abandoned because if the round is backed into the shell, the shell protects a layer (or bands) of lube on the bullet. The modern style is also sealed better against moisture, and resists having the round dislodge from the shell.

As the 38 round was modernized, the shell width was retained but the bullet diameter was dropped so it could back into the shell, and the barrel shrunk to match. But for marketing purposes, they didn't want to admit they'd dropped from a 38 to a 36.

Until in 1937, some marketing genious came up with the magic words "THREE FIFTY SEVEN MAAAAAGNUM, BABY!" and honesty (sorta) returned .

The 45LC was never heeled, it was in fact one of the first of the modern-type "backed into the shell" types (1873). So the bore numbers always were honest. 44s on the other hand started as the previously mentioned 44 Henry Rimfire heeled, and suffered the same "bore reduction" that the 38 went through (for the same reason) and is now .429.

 

[mummac]

Thank you.

 

[farscott]

Mr. March,

Thanks for the explanation; it dovetails nicely with what I was taught. I do have a few questions about rounds that were designed at the same time as the .45 Colt.

How did the .44-40 (.44 WCF) end up with a 0.427" (not 0.429") bullet? Has anyone ever determined if the .38-40 (.38 WCF) was really supposed to be named .40-38 (a 0.400" bullet ahead of 38 grains of black powder)? Did Winchester just mess up on the marketing? Was it supposed to be the .40-40? Was it a deliberate effort to mess with the competition?

 

[mummac]

Also, if anyone can suggest a book that has the history of different cartridges, I would greatly appreciate it.

 

[MrAcheson]

Why would .38-40 become .40-38 if the powder charge is still 40 grains of BP (in the old balloon head cases at least)?

 

[ARGarrison]

Mummac;

Try "Cartridges of the world" by Frank C. Barnes.

Ordered my copy through a catalog, but I have seen them at Barnes and Nobles sence.

 

[Mal H]

Get a copy of Frank Barnes Cartridges of the World. It's the best available cartridge reference around.


[Edit]
ARGarrison, great minds and all that ...

 

[farscott]

Why would .38-40 become .40-38 if the powder charge is still 40 grains of BP (in the old balloon head cases at least)?

I had heard that the original black powder charge might have been 38 grains of black powder, not 40 grains. I have not been able to find an authorative answer to the origination of the .38-40 nomenclature.

 

[CWL]

Prior to metallic or conical bullets, guns and their bore were designed & sold by how many round bullets could be cast from a pound of lead. This was a standardization back when firearms were all handmade.

This shot/lb weight ratio carried over to modern firearms and is the basis for the various basic calibers that we have today.

 

[arinvolvo]

Jim, you never cease to amaze me with your knowledge. *bows*

 

[Jim March]

Thanks, but I have no clue as to the history/origins of the 38-40, 44-40 and suchlike. There was probably a heeled ancestor in there somewheres .

I wonder why they retained the shell diameter instead of the bullet diameter? I know that in the old days, shells were a real pain to make, so...hmmm...maybe keeping the tooling for shell making was more critical than the tooling for bullet molds and barrels?

 

[Jim March]

How much you wanna bet some of these exact calibers (.456, .454, 357, etc) were a product of what bits the tool'n'die makers were producing? Or had on *sale* when the guy was first designing the gun?



That in turn let to military purchases, which led to bore and bullet component compatibilities, competition classes, much later legal limits, etc?

Sheesh.

It's like asking why the space shuttle's two smaller booster rockets were the width they are. It's because that's the width of a Roman chariot.

You think I'm kidding? The chariots led to road specs. Everybody copied that axle width, so they were all using the same ruts. That led to the standard railroad gauge. Which led to a certain max size for railroad cars. Which the shuttle boosters had to fit on.



That's over 2000 years worth of this sort of standardization .

 

[BigG]

I believe 44 Russian was the first cartridge that used the smaller .429 bullet that the 44 now comes in standard. That's because the Russians spec'd an inside lubricated bullet. The 44 American had the heel type bullet and that was what they tried to sell the Ruskies. So S&W took the American case and put a bullet that would fit inside. It happened to be .429.

The older 38s were outside lubricated and larger than .357, as Jim said. I think .375 or .379? Brain fade...

 

[Jim Watson]

You need to take it back a step farther.
I don't know how Sam Colt arrived at a nominal .36 caliber in the first place, but once he had, he drilled a .36" hole in a barrel blank. Then he cut rifling grooves in it. Deep rifling, to get a grip on a soft lead round ball. And then made a cylinder with chambers to hold a ball to fill those grooves. And hung a rammer lever under the barrel to push them in tight to seal the chamber mouth against flashovers. That took a .376" ball or thereabouts.
Likewise a .44 cap and ball revolver took a .451" or so ball. But "caliber" was originally defined as the *bore* diameter. Going by groove or bullet diameter came later.

Then when the newfangled brass cartridges came out, they were using the heel bullets and they made bullet and brass the same diameter as the percussion guns' balls. They had to, a lot of the early guns were converted from percussion or made up with left over percussion parts. So a .36 became a .38 - no need to get people to try to remember three decimal places - going by brass & bullet diameter. The .44 was a little more complicated. A Colt conversion takes .44 Colt, a Remington conversion is a .46!

When Colt came out with the SAA, they enlarged the case to hold the .45" bullet diameters of the cap and balls and conversions. It was an all-new gun and they could make the cylinder large enough to hold it. When S&W came out with the .44 Russian and eventually the .38 Special, they kept the case & chamber diameter and reduced bullet diameter, possibly because they were working with existing model guns with established cylinder diameters and wall thickness no more than necessary for the original caliber.

Approximately. Tool availability, 19th century manufacturing tolerances, and tweaking of design by actual shooting shifted actual measurements a bit, but I think I've got the logic straight.

I don't know what Winchester had in mind when they designed the WCF series. Those guns are just strange.

 

[Johnny Guest]

When I first began reading this thread - - -

- - -I started mentally composing a reply. Upon reading the whole thing, I find that Jim Watson and Jim March had written pretty much every single thing I know on the subject (and probably a bit more. )

Nice replies, guys. The evolution of firearms and their ammunition is a broad and interesting topic, probably influenced at least as much by convenience, happenstance, and art* as by logic and science.

To slightly expand on CWL's comments, this is the origin of the terms "gauge" (or "gage") and "bore" for shotgun measurements. If you could cast sixteen round balls from a pound of lead, the gun bore which would accept them was termed a sixteen guage (or bore.) Same with most of the other shotgun sizes, right down to 28 gauge. I'm sure most here understand that a .410 shotgun is NOT "four hunnert and ten gauge," but properly a .410 inch bore. I understand the 9mm bore shotgun used to be popular for garden pest control in Britian and in Europe.

Best,
Johnny

*No, not THR Moderator Art Eatman. He's an, uh, a MATURE individual, but not really THAT senior.

JPG

 

[Jim K]

In the beginning

I doubt that anyone today knows why Colt chose .36" or .31". The .44" was needed by the army because the small .36" was ineffective in shooting horses, something normally done (though never shown in movies) when faced with a cavalry charge or in a cavalry battle. But why .44? Again, no one knows.

But it happens that we know the reason one common U.S. caliber was chosen. When plans were being made to replace the "trapdoor" Springfield with a smaller caliber repeating rifle, Frankford Arsenal was asked to develop the ammunition first. This was normal practice; once the required characteristics of the ammo were worked out, rifles could be made for the ammo and ammo could be made and furnished for rifle tests.

Some time later, the fellow (I now forget his name) who chose 30 caliber was asked the reason for his choice. His reply was that that caliber seemed to meet the requirements but mainly that "it was a nice round number."

So much for physics, mathematics, ballistics, etc. The caliber of U.S. military ammunition for nearly a century was set because 30 was a nice round number.

Jim

 

[Hal]

Jim,

I don't know how Sam Colt arrived at a nominal .36 caliber in the first place

It was exactly like CWL says. The caliber, .36 was the measurment based on the number of round balls that could be cast from a pound of lead for that caliber.

IIRC. .36 cal translates to 100 to the pound.

 

[Jim Watson]

True, a .36" lead ball is right at 100 to the pound.
BUT a .36 Colt actually shoots a .376" ball, which is where the .38 cartridge designation eventually came from.

There may be something to the "even gauge" scale, though. Our ancestors were not much hung up on the decimal system anyhow. Thomas Jefferson managed to promote decimal currency, but his plan for decimal weights and measures, NOT the same as the French metric system, did not fly.

The even gauge scale can start with the British Brown Bess musket. It was a nominal .75 cal but with plenty of windage around a .73" ball it could be considered a 12 gauge. Likewise the French and American .69 muskets were pretty much 16 gauge. And .54 may have been common for rifles because, with space for a patch, they would shoot a half-ounce ball. A muzzle loading .44 is firing a patched quarter ounce ball, but the .451" ball for a so-called .44 cap and ball revolver is right around 1/3 ounce. And that .376" ball for a .36 Colt? About eighty to the pound, 1/5 ounce.

 

[BigG]

Jim, good info, but added more fog to the subject than illumination.

As you or somebody mentioned earlier, I'll bet it was the availability of tooling that was the driving consideration.

Colt Patersons came in .28, .31, .34, and the big mama belt model .36, AKA the TEXAS PATERSON, IIRC.

I do remember reading old books about Kentucky Rifles and sich that never spoke of caliber but said the rifle fired a ball of so many to the pound. I would think caliber is a recent development that we rely on today whereas our forefathers did not.

 

[Jim Watson]

It was certainly the custom to describe a gun by gauge rather than caliber, but you are working in two eras. Colt revolvers were industrial products made with the Whitney concept of standardized and interchangeable parts. Some were even made BY Whitney. To do that you have to have accurate measurement. They used a lot of purpose made go-no go gauges rather than micrometer measurements, but everything was made to a standard. Maybe the first barrel was from whatever reamer they had on hand but the rest had to be the same.

The Pennsylvania-Kentucky riflesmith, on the other hand, probably didn't worry too much about the exact caliber or gauge of a muzzleloader. By the time he had his handmade reamers sharpened and adjusted and a barrel completed with them, he was just glad to be done. But he still needed to be reasonably close to his own standard, he had to furnish a bullet mold and he sure didn't want to have to grind a new cherry for every job.

Getting down in the small calibers of the Pattersons and the Roots, you are talking about hundreds of balls per pound. Hard to keep track of nominal gauge then.

 

[BigG]

The old ammunition boxes like for semi-fixed revo ammo would be labelled sumpin like "6 Cartridges for Colt's Navy Revolver," IIRC. True, Jim, I was talking about two different eras and two mfging methods.

The frontier bbl maker was more of a blacksmith, winding an iron strap around a mandrel and welding it into a tube. Colt's bored out their bbls from a raw forging, most likely. Very interesting and enlightening conversation. Thank you!

 

[Jim Watson]

True, the Kaintuck was made by forge welding around a mandrel, an early version of Damascus or Laminate construction. But the rough tube still had to be drilled or bored, reamed, and rifled, with such machine tooling as could be made in the same shop.

Usually forged to rough octagon shape and then ground on a big grindstone. The visible flats would then be drawfiled smooth, but the bottom flats concealed under the stock would often be left with grindstone marks. Easier to hammer, grind, and file an octagon barrel than to make a round one if you don't have a good lathe.

Colt percussion revolver barrels were indeed made from forgings, as described in a contemporary magazine article by Charles Dickens!

 

[CMcDermott]

The absolute weirdest are the winchester centerfire's introduced for the Model 1873 levergun. 32 WCF = .312" bullet, 38 WCF = .401" bullet and 44 WCF = .427" bullet. All of these cartridges were new designs not based on any previous design, and none of them match the name with the caliber. And there isn't any accepted story of why they were named the way they were by Winchester. The 32-20, 38-40 & 44-40 names were started by Marlin a decade later when they introduced the 1894 in these calibers. All of the other cartridges that are mis-matched either were based on a heeled bullet cartridge design, or used bore diameter instead of groove (bullet) diameter for the name.