Re: .308, 30-06. 45-70 etc etc Newbie
Generally, the first two or three digit number is the diameter of the bullet. The other numbers let you know which one of the many 30 caliber or 35 caliber or whatever it is.
Some go back to black powder usage. 45/70 is a 45 caliber bullet loaded with 70 grains of black powder. 44/40 is a 44 caliber bullet over 40 grains of black powder. But that does not always apply. 30/30 is not 30 caliber over 30 grains of powder, although many people will tell you that's what it means. It was always a smokeless powder cartridge, but in the early days of smokeless powder, few people knew exactly what to expect of it. 30/30 is a 30 caliber bullet loaded like it has 30 grains of black powder. It has the velocity and knockdown of a 30-grain black powder load. People knew what that meant.
It's the same with shotshells. You see boxes of shotgun shells marked 3 1/4 dr. eq. That means 3 1/4 dram equivalent. A dram is 1/16 of an ounce. 27 1/3 grains. 3 1/4 drams is 90 grains, so a shotshell loaded to 3 1/4 dram equivalent means it will act like a shell loaded with 90 grains of black powder. Black hasn't been used in shotshells for decades, but when they first started using smokeless they put "Dr. Eq" on the box, to help the hunters know how strong the shells were, and they still put it there.
Sometimes, though, the second number has nothing to do with the powder.
300 Savage is a 30 caliber cartridge designed for use in Savage 99 rifles. They necked it down to 25 caliber, and this new round would go 3000 feet per second. That was mighty fast, back in the early 1900s. They called this new round the 250/3000 - 25 caliber, 3000 fps. They later necked that down to 22 caliber, and called it the 22/250.
In 1903 the military designed a new rifle - the 1903 Springfield - and a new cartridge for it - the 30/03. 30 caliber, for the 1903 rifle. Three years later they redesigned the cartridge, and it became the 30 caliber of 1906 - 30/06. Also generally called the 30/06 Springfield because that was the first rifle it was used in.
So, basically, the first number is the diameter. Not always precise (44 magnum is not 44, it's 43. 38 special is not 38, it's 36), but pretty close. The second number (or word) can mean pretty much anything. You just have to learn them.
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