I understand the gauge system and I am not talking about that. What I want to know is why are the bores of firearms drilled out to such weird fractions, e.g. .44, .22, .303, 7.92mm, etc.? Were these chosen because of some desirable ballistic qualities arrived at through experimentation? Were they the result of scaling down some other common caliber or gauge?
Thanks,
Rob
(I believe I may have asked this question here before, but I was unable to find it.)
Sort of.
Gunsmiths have spent centuries trying to find a “perfect” round for each purpose. They try to balance the qualities of a round’s weight / mass, shape, and propellant to achieve whatever outcome is most desirable for their goal. There is no particular rhyme or reason for why a projectile ended up a certain diameter, except to say that at some point a gunsmith thought he would get better performance if he added or subtracted a few hundredths of an inch.
Which ones “stuck” largely depended on the performance of the munition and the popularity of the firearm.
The weirdest part is that the name of the munition is often completely unrelated to the actual diameter of the bullet. For example, a .357 magnum and .38 special have the same diameter and are virtually interchangeable. Sometimes the munitions were named after the exterior diameter of the casing, the inner wall of the chamber, or whatever other random part of the gun the smith decided to measure.
Some help?
The full explanation is a very long but interesting story. Unfortunately, there is no way to go one by one and explain why each bullet/cartridge is the way it is.
The short version is that there are literally thousands of different bullet/casing/powder combinations that have been developed and adhering to round numbers on whatever diameter scale you want to reference generally isn’t a big priority to the people that invent them. Most popular bullets like the .30 caliber that are still used in lots of guns like the 30.06 are quite old and were chosen because there was some legacy supply of barrels and/or bullets already made for that size round.
Once the full cartridge (that includes the bullet, case, powder, and primer) became popular, it was inertia through popularity that kept it at that size. Gun makers built more guns to support the round and ammo makers made it easy to buy bullets in that caliber so the preference continued. It is the same as any other standardization of any parts even if they measure in sizes that don’t cleanly match any particular measuring system.
There are some other side issues however. Some gun cartridges are misnamed. A 38 Special handgun round and .357 Magnum actually use interchangeable bullets of the same size. You can fire 38 Special cartridges from a .357 Magnum with no problems but not vice versa because a .357 Magnum is a lot more powerful than a 38 Special and would probably cause a catastrophic failure even if it can accept the cartridges.
You almost have to go round by round to understand the full reasoning behind them. For instance, the 30.06 was wildly popular partly because it was a military round at one time but also an excellent hunting round. Experimenters wondered what would happen if you used the already successful case and narrowed the neck down so that it could fire a smaller bullet. The result was the moderately successful 25.06 that is great for deer hunting.
For every cartridge that became successful in the marketplace, there were literally hundreds more developed by the military, gun companies, and hobbyists. Many of those are at least as good as more popular rounds but didn’t catch on for whatever reason. It is like a computer hardware/software problem. You can develop anything you want but it doesn’t matter how good it is if you don’t have the user base to sustain it in the marketplace.
The big difference is that home reloaders can support their own oddball cartridges if they really want to and there are many oddities out there. Even ammo companies produce limited runs of lots of cartridges most people have never heard of because there are a enough users to make it worthwhile.
Don’t overlook the standard sizes of ball shot. Double-ought buckshot is, well, 00 gauge shot.
Which is often fired from a 12 gauge shotgun, so named because a ball of lead 1/12 of a pound is that diameter. Ditto for 20 gauge, and the now rather rare 10 gauge - 1/20th and 1/10th of a pound balls, respectively. Then there’s the .410 shotgun, with a barrel diameter of…
And you’ll never guess what gauge ball a BB gun shoots…
ETA: AFAIK, these are all different gauge scales, but I could be wrong…
What I am getting at is that when I look in my toolbox, I don’t see a .357" bit, a .22" bit, etc. Why were these sizes picked? Chicken Legs’ post seems to blame the whole thing on Sam Colt, or inch representations of various gauges. A corollary question is what was the first standard caliber that you could buy off the shelf bullets or cartridges for?
Tools, sockets, etc. come in standard, regularly-spaced sizes because there is really only one dimension that matters - the width - and the rest of the dimensions can be scaled up from that. A 15mm nut is just a scaled-up 10mm nut - that single number is all you need to know about the nut’s shape. And 1mm is all the variation anyone needs - there are no circumstances where a 14mm is too small, and a 15mm too big, so you really need a 14.5mm.
Firearms cartridges are referred to with a single number for convenience sake, but unlike with tools, that number is far from the only one that matters. There are all kinds of little shapes and dimensions on the cartridge and bullet that that matter. The whole design for a cartridge is referred to by a number that corresponds roughly to the outside diameter of something, but there are probably around 15 or 20 other dimensions that are just as important.
Here is a diagram of the .30-06 Springfield. File:.30-06 Springfield.svg - Wikipedia All of those dimensions are important for the cartridge to function properly.
It is not that someone sat down and said “Well, we need some standard firearms sizes, so here goes: .22, .30, .357, .38, .40, .45, 9mm, 10mm, .50, done!” Over time, people designed thousands of different cartridges, for a variety of different reasons and a variety of different purposes, with a variety of different features, and named them by picking some designation loosely related to some measurement on the cartridge, that was notably different from other designations in use. Some of these designs became popular, others didn’t.
Since cartridges are chosen for many reasons and purposes others than just size (bolt-action target rifle? revolver? semi-auto handgun? semi-auto rifle?) , and their names don’t really correspond to any standardized size specification anyway, the numeric sizes in firearms cartridges show no semblance of organization.
Bolts and sockets, on the other hand, are chosen only for their lateral size, and their shape is entirely specified by their lateral size, so a nice, orderly set of standard sizes is expected.
The part you are missing is that there is no adherence to any specific diameter when designing a new cartridge or bullet. You design it first, test it, and describe it later usually on several different scales. What those specific diameter measurements end up being is of no importance especially when they are being translated both historically and geographically. There is no metric system or any other standard for bullets except for describing them after after they are already in production. Some of them have metric names like the 9 mm, some have a name describing the caliber like the 30.06 with additional information attached like the year of development (1906 in that case) and some have nicknames like .220 Swift (one of the fastest cartridges in the world). There is no one standard for it.
If you want a succinct explanation, there is none for this question. That is what we are trying to tell you. Designers build the best cartridges they can without regard to any round numbers and then name them after the fact. Even then, some of the names get translated into raw numbers in other systems that don’t mean much.
You asked about 7.92 bullets in your OP. Here is the story on why those exist and it is complicated Firearm technology is old and predates the adoption of the metric system in most countries. Other systems still exist as well. If you want a clean answer on a particular round, we can give you one but otherwise you are just going to have to accept the fact that we are dealing with legacy standards that don’t always make much sense unless you consider the entire context and goal.
If you want to know why bullets have never been made to follow the metric system, the answer is that there is no point to that. Firearms are about the most stable tools ever manufactured and can still be used reliably 100 years or more after they are built and cartridges last almost as long. There is no need to replace something that isn’t broken just to satisfy people that like round numbers based on modern scales.
Sorry for my impatience. I grew up studying guns and have shot everything under the sun many times and owned most of them. What seems obvious to me probably isn’t to many people especially these days.
Let’s say you did have a standard for bullet size and a 30 caliber bullet was standardized to some metric type measurement. What good would that do? You have many different types of guns that fire that same range of bullet. In popular current use, you have a 30-30, .308, and 30.06 just for starters. Even if you know the bullet diameter perfectly it still tells you nothing about whether that cartridge as a whole can be fired in any particular gun. Hint: it would be bad news if you tried to force a small 30-30 rifle to fire a 30.06 round somehow. They are vastly different firearms even if they do fire roughly the same caliber of bullet.
You still need distinct names for each cartridge so that they aren’t confused. It is almost always impossible to make firing mistake because cartridges made for one firearm usually will not fit in another but there are a few exceptions.
The bullet measurement is not that important and is only one part of the overall design. Every one still need a distinct name or way to identify it. There is nothing special about this. I bought a 12" windshield wiper for the rear of my vehicle tonight. It didn’t fit because I bought the 12-B model instead of the 12-A model by mistake so I had to exchange it. Neither one of them are 12" exactly. Most manufactured products are that way.
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As with most of engineering, it is about various trade-offs. Here is a modern example:
Say you want ammunition that can penetrate 1.6mm titanium plate and 20 layers of kevlar at distance of 200m, when fired from 200mm long barrel. At the same time, it needs to be short enough to fit into a handgun grip. It should also be fast to have a flat trajectory. And it needs to be heavy enough to kill a person, but light enough for manageable recoil during automatic fire, etc., etc.
Put it all together and you get a reasonable compromise: FN 5.7 x 28mm
While development of older ammunition was not always so scientific, it always involved a number of opposing requirements.
Sure you do, it’s called a 9mm bit!
I think what the OP is getting at is why it’s 7.92, and not just straight up 8mm. Or why it’s 7.62 mm and not 7.5 or 7.75? Or .357 instead of .35?
A lot is due to the differences in measuring- some measured the diameter between the lands of the rifling, while others measured between the grooves. For example, the British .303 barrel is .303 between the lands (7.62 mm) but .311 between the grooves (7.9 mm). Bullet diameter is .311, or 7.9 mm.
US .30-06 bullet diameter is actually .308, or 7.8 mm, while the bore diameter between the lands is a lot closer to .30, or 7.62.
Paper cartridges were in common use in the mid-1800s. Civil War soldiers used paper cartridges in their muskets, and handgun ammunition was readily available. Here are some paper cartridges I made. The soldier would bite open the end of the cartridge and pour a little powder into the barrel, then close it up and ram it down. (I suppose they might have dumped all of the powder, bout really you just want enough powder to take a spark.) I gather that shooters would prick the ends of their revolver cartridges to accomplish the same thing.
Paper cartridges used nitrated paper so they would light easily and burn completely. Musket cartridges were protected with bee’s wax that also lubricated the ball. Once the cartridge was seated, a percussion cap was placed on the nipple. The hammer struck the cap, and the flame travelled down the nipple into the chamber to ignite the powder. I never prick my revolver cartridges; just crushing them into the chamber with the ramrod is enough, and I soak the cigarette papers in saltpetre (and dry them) so that they’ll burn well. All of this pricking/biting, ramming, and capping may seem a bit tedious compared to using breech-loading metallic cartridges that have the integral primer (analogous to the cap), but it was faster and safer than measuring powder for each shot. (You should measure the powder into the muzzle rather than pouring it from the horn or flask because a lingering spark would ruin your day.)
I know the question assumed metallic cartridges; but paper cartridges existed before them, and were called ‘cartridges’.
So, lemme sum up, both from my own knowledge and what’s been said here. There’s an evident expectation that bullets would be some “standard” measurement - an even fraction, or an even decimal - but few are. I posit, as summary, that this is because:
[ul]
[li]A skilled and/or scientific gunsmith has other considerations than simple diameter when designing a new caliber and round. Convenience is not a factor.[/li][li]Many older calibers come from archaic measurements like the gauge/ball system and older measuring systems that don’t translate neatly to inches or millimeters.[/li][li]Some newer calibers start with a nominal standard measurement, but adjustments for land and groove compression and perhaps fine-tuning of the load result in an odd number.[/li][/ul]
Did I miss anything?
With the older flintlocks like the Brown Bess and the French Charlevilles (Napoleonic Wars and U.S. Revolutionary War) the typical procedure was to bite open the end of the cartridge, pour a small amount of powder into the pan to prime it, close the frizzen, then dump the rest of the powder down into the barrel. With Civil War muskets like the 1853 Enfield and 1861 Springfield the soldier would dump the entire powder load down into the barrel. It was a big improvement over measuring each powder load from a powder flask using a powder measure and dumping that down the barrel but you’re still talking 15 to 20 seconds to load the weapon even once you’ve had a lot of practice and are moving as fast as you can.
Revolver cartridges, as you stated, were typically inserted whole into the chamber.
Musket cartridge for a smooth bore round ball type musket:
Musket cartridge for a Minie Ball type rifle-musket (note the top version is cut away so that you can see what is inside it):
http://www.treasurenet.com/forums/attachments/what/508686d1332451407-what-bullets-were-fired-1863-springfield-58cartridge-1-.jpg
Note the difference between these cartridges and the revolved cartridges in Johnny L.A.'s links which have the round exposed at the end. His are typical of revolver cartridges from that period.
Some of it is marketing. A .38 special has the same diameter as a .357 magnum. The 7.92 Mauser is also called 8mmm Mauser. Same bullet.
I don’t suss “marketing” in this example - it would seem that some larger number would convey power, rather than the other way around. Or was the alternate number chosen just to differentiate the rounds in marketing terms?
There were already a number of .38, .38 Super, .38 S&W, .38 Special. .38 Short Colt etc, and oddly, .38 is actually closer to .357, so .357 right. But early .38 used a no longer much used “heeled bullet” where the internal diameter of the barrel= that of the cartridge case. So, they were .38. Note that rimfires such as the .22 Long Rifle is still a heeled bullet.
Note that a .44 is actually more likely to be a .429 due to this.
I am guessing that there are a few folks who have never worked on vintage British Motorcycles or cars. Your analogy is actually flawed, because similar things happened in the world of fastenings, whereby thread shaft diameter and AF sizes may well be non-standard, not to mention thread pitch, thread depth, engineered fitted bolts etc.
Nut and bolt sizes were developed for many purposes, from pure strength to resistance to vibration of many levels and frequencies including both mechanical and electromagnetic vibration, restricted access, heat expansion, varying types of torque tools, ease of use in automated manufacturing, the ability to lock in place, or ability to adjust by small increments
There is a world of fastenings that is pretty near as complex as that of gun diameters
