Tuesday, April 27, 2010

So, why is the .38 Special only .357 in diameter?

Over at his place, Jay put up a quick-and-dirty explanation of caliber. Seeing that, I got to thinking about the age-old question "Why are .38 Specials only .357 in diameter?"

That is the Age-Old Question, isn't it?

I knew it had something to do with conversion from cap and ball to cased bullets, and I thought I heard something about conversion from black powder to smokless thrown in somewhere, but I really didn't have it all together. If someone were to ask me the Age-Old Question, I wouldn't be able to answer it to my satisfaction.

So, I started digging around the Intertubes. My search started, naturally with the .357 Magnum. Just kidding. It started with the .38 Special, which led me to .38 Long Colt, which in turn led me to .38 Short Colt. All this led me, finally to the explanation I was looking for. It was there all along, mentioned in each article - the heeled bullet:

Many shooters wonder why a .38 caliber firearm actually shoots bullets of diameter .357 inches, and a .44 caliber firearm shoots .429 inch diameter bullets. In both of these cases, the name of the caliber derives from older heeled-bullet designs, and the name was kept even when the bullet was shrunk to fit inside the case. The .38 S&W cartridge, for example, dates to 1877 and has a nominal outside case diameter of .380 inches, while the inside of the case is .357 inches. Older .38 caliber cartridges, like the .38 Long Colt, did use a heeled bullet, so rather than create a new ".35" or ".36 caliber", Smith and Wesson kept the designation ".38" even though it no longer accurately reflected the bore diameter.

There you have it!


Linoge said...

Huh. One of life's great mysteries answered - thanks! :)

Wai said...

I would have felt better if they kept it real.

mariner said...

So the short answer is:

Cartridges were once designated by outside cartridge diameter.

When this changed to designating cartridges by the bore diameter of the firearms they were used in, some cartridges kept their old designations, for historical reasons.


Billll said...

Before cartridges, there was the smooth bore which was measured in gage. 50 gage lead balls are .454" dia, hence the .45. 100 ga balls are .357 dia. I seem to remember that 60 gage is .429". I built a spread sheet of this once, and posted it.