[Blakenzy]

I overheard a conversation today concerning the .38 Special revolver/cartridge:

"it fires a .357" bullet but it was named .38 because the chambers in the cylinder measure 0.38 of an inch in diameter."

I don't have a .38spl on hand, but I measured a .357mag and the cylinder's breeches are around .37-.38", so... what's up with that?

[General Geoff]

.38 I think is the diameter of the cartridge casing.

[Oro]

but it was named .38 because the chambers in the cylinder measure 0.38 of an inch in diameter."

1/2 way true. The "parent" cartridge of the .38 Special was originally the .38 Short Colt. It used a "heeled" bullet which had a diameter of about .38 (same as it's cartridge diameter, as Gen. Geoff said). But it started with the .38 Short Colt and the name stuck with each generation until the .38 Special came along.

The original bullet diameter of the .38 Special was .358", not .357, anyway. .357 is the size of later jacketed/sj projectiles, not lead ones. At the time of introduction, they called it .357 because it sounded cool, not because that's what the bullet diameter was. Cartridge names are almost always a little off when you actually look at the details - rifle, pistol, doesn't matter.

[1911Tuner]

Almost there...

.357 indicates (nominal) bore diameter. Lead bullets are typically sized a little over bore diameter to effect a gas seal.