The specifications for all varieties of “9mm” cartridges (9x17, 9x18, and 9x19) actually call for a projectile with a diameter of 0.355 inches, which is actually 9.017 millimeters.
Similarly, the specification for .38 Special calls for a projectile with a diameter of 0.357 inches.
If you measure the barrel of any firearm chambered in any variety of 9mm, .38 Special, or .357 Magnum, you’ll find that they’re all ostensibly .35 caliber (0.350 inches).
Why? Well, the simplest answer is, things aren’t always what they’re called. In the world of cartridge designations, there are many, many such idiosyncrasies; these are only scratching the surface. I find this interesting because many people perceive cartridge designations as being very uniform, logical, and standardized, but the actual truth is far from that.
In some cases, the number is even made bigger just to make it sound more powerful, such is the case with .460 S&W Magnum, which is a more powerful version of .454 Casull, which itself is a more powerful version of .45 Colt, all of which actually fire a projectile with a diameter measuring 0.452 inches.
The barrels smallest diametral dimension has to smaller than the bullet, otherwise the rifling wouldn’t engage.
Is that what the 0.350" are referring to?
It’s also kinda funny how the most common rifle rounds are smaller calibre than 9mm, so if you ignore all the other metrics, most handguns shoot “bigger” bullets than most rifles.
The barrels smallest diametral dimension has to smaller than the bullet, otherwise the rifling wouldn’t engage.
Kind of, but not really. The bullet actually slightly expands from heating. At the same time though, if you measured the diameter of a cold barrel and a hot barrel you would get two different measurements. If the cold barrel is too tight of a fit the bullet has an increased chance of lodging when it heats up and expands.
This is why bullets moved towards copper jackets with some sort of other metal center chosen for various justifications. The copper jacket is soft, east to expand into rifling grooves, not hard enough to damage and wear out rifling, and can stretch a little if it gets too tight.
Really, the BIGGEST difference is going to be the casing, chambering, and pressure. It’s like how people talk about 5.56 and .223 being the same. They are the same only at face value of size and chambering, but very different on rated pressures. A rifle rated to shoot .223 should only shoot .223. A rifle rated to shoot 5.56 is rated for a higher pressure and can shoot both.
In the same regard to OP: 9mm, .357, and .38 special may measure the same, but all 3 chamber very differently and have different pressures.
Hell, even 9mm has 9mm luger (parabellum) vs 9mm NATO. it’s the same round/casing, but again, different pressure. A gun that shoots luger (lower pressure) should never shoot nato. But a gun that shoots nato (higher pressure) can shoot both.
It’s also kinda funny how the most common rifle rounds are smaller calibre than 9mm, so if you ignore all the other metrics, most handguns shoot “bigger” bullets than most rifles.
True, but this is also why “stopping power” is then measured in ft-lb (foot-pounds) or joules for metric. Pistols may shoot bigger rounds, but at significantly slower speeds. Less powder for recoil control and less barrel length for pressure build up. The bigger size bullet is a compensation for the smaller gun. A rile with a smaller round has far more energy behind it’s round.
The specifications for all varieties of “9mm” cartridges (9x17, 9x18, and 9x19) actually call for a projectile with a diameter of 0.355 inches, which is actually 9.017 millimeters.
Similarly, the specification for .38 Special calls for a projectile with a diameter of 0.357 inches.
If you measure the barrel of any firearm chambered in any variety of 9mm, .38 Special, or .357 Magnum, you’ll find that they’re all ostensibly .35 caliber (0.350 inches).
Why? Well, the simplest answer is, things aren’t always what they’re called. In the world of cartridge designations, there are many, many such idiosyncrasies; these are only scratching the surface. I find this interesting because many people perceive cartridge designations as being very uniform, logical, and standardized, but the actual truth is far from that.
In some cases, the number is even made bigger just to make it sound more powerful, such is the case with .460 S&W Magnum, which is a more powerful version of .454 Casull, which itself is a more powerful version of .45 Colt, all of which actually fire a projectile with a diameter measuring 0.452 inches.
The barrels smallest diametral dimension has to smaller than the bullet, otherwise the rifling wouldn’t engage.
Is that what the 0.350" are referring to?
It’s also kinda funny how the most common rifle rounds are smaller calibre than 9mm, so if you ignore all the other metrics, most handguns shoot “bigger” bullets than most rifles.
Kind of, but not really. The bullet actually slightly expands from heating. At the same time though, if you measured the diameter of a cold barrel and a hot barrel you would get two different measurements. If the cold barrel is too tight of a fit the bullet has an increased chance of lodging when it heats up and expands.
This is why bullets moved towards copper jackets with some sort of other metal center chosen for various justifications. The copper jacket is soft, east to expand into rifling grooves, not hard enough to damage and wear out rifling, and can stretch a little if it gets too tight.
Really, the BIGGEST difference is going to be the casing, chambering, and pressure. It’s like how people talk about 5.56 and .223 being the same. They are the same only at face value of size and chambering, but very different on rated pressures. A rifle rated to shoot .223 should only shoot .223. A rifle rated to shoot 5.56 is rated for a higher pressure and can shoot both.
In the same regard to OP: 9mm, .357, and .38 special may measure the same, but all 3 chamber very differently and have different pressures.
Hell, even 9mm has 9mm luger (parabellum) vs 9mm NATO. it’s the same round/casing, but again, different pressure. A gun that shoots luger (lower pressure) should never shoot nato. But a gun that shoots nato (higher pressure) can shoot both.
True, but this is also why “stopping power” is then measured in ft-lb (foot-pounds) or joules for metric. Pistols may shoot bigger rounds, but at significantly slower speeds. Less powder for recoil control and less barrel length for pressure build up. The bigger size bullet is a compensation for the smaller gun. A rile with a smaller round has far more energy behind it’s round.