.357 caliber is 9mm.
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Well to be nit-picky, 9mm bullets are typically .355.
You are pretty close. If my math is right then if you convert .357 inches to millimeters you get
.357 inches = 9.0678 millimeters
And the 9x19 parabellum round is actually 9.017 mm or .355 inches.
And for some crazy reason the .380 is actually .355 inches...
go figure.
Some rounds measure by casing and some by bullet and some just make no logical sense but have their foundation in how they relate to some other round or its history of development. For example the 30-30 uses a .308 bullet, but the second 30 came from the early loads of 30 grains of powder...and the 444 Marlin’s name is due to it being a derivative case of the 44 magnum with .429 bullets and so on it goes...
9mm=.355” and includes 9mmParabellum/luger, 380 acp and 357 SIG, as well as a plethora of older obsolete cartridges. .357 is 38 cal, and 38 SW, long and short colt etc, 357 mag and max and others wear that bullet diameter.
9mm makarov is an oddball at .366”(or so... pistol dependent).
So, no, .357 is NOT 9mm caliber.
SAAMI and CIP state the actual measurements for US and International purposes of uniformity etc.
You proved my point. Thanks.
.357 caliber is 9mm.
.
Almost but not quite. 9mm bullet is .356 and the 38 spl and .357 mag are actual .357.
Should have read further in the comments. Others have “corrected” your statement so I’m sure you’re tired of hearing about it. That being said I’ve sized 125 gr .357 bullets and used them fine in the 9mm S&W, tragically lost in a canoeing accident of course. ;-)