ACTUAL SIZE OF WEAPONS

[williamlayton]

I have been ordering things to reload my weapons and, believe it or not, the big decisions have been on bullet size. I do not think that I ever stopped to consider this.
For instance:
.45 = .451 maybe.
9mm= .355 or .356???
Well you get the idea. When ordering bullet onethousandth of a inch may not seem like much, and really is not, but, why the difference in sizes and what is the actual size of each. Maybe there is not an actual size, from manufacturer to manufacturer.
Lets see if we can come up with theoretical sizes for:
9mm
.38
.357
10mm
.45
9x23
38 super
.44
Or others.
Why are bullets offered in sizes that are a bit larger or smaller than I considered them to actually be?

Blessings

[PA-Joe]

Another question is, have you slugged your barrel and do you know what the actual grove diameter is? You have to match your actual barrel diameter to the correct bullet. That is why you test different loads and combinations.

Another factor is the actual thickness of the case. Some manufacturers use thin metal while others are a little thicker.

[winman]

Not to mention the 7.62X39.  Some are .308 while others are .311.  A difference of three thousanths!  Seems like a lot to me, especially with jacketed bullets.

Yet some people say they are interchangeable, and it doesn't really matter.  I  have never understood this.

How can that be?

Edit:  On the other hand I just saved a bunch of money on my insurance by switching to Geico - NOT.

[Reed1911]

9mm - .355"
.38 - .357"
.357 - .357"
10mm - .400"
.45 - .451 to .452"
9x23 - .355"
38 super .356"
.44 - .429"
Or others.
Why are bullets offered in sizes that are a bit larger or smaller than I considered them to actually be?
 Different bullets will be +/- .0005" variance depending on manf. tolerance. Some calibers like the .38 Specal are so named for the O.D. of the case at the mouth, while some like the .357 are so named for the bullet diameter. Also you will usually find that cast lead bullets will run .001" larger than the jacketed counterpart. Provided starting loads are used you find that a slight increase or decrease in size will perform better in your gun (e.g. using a .356" jacketed bullet in a standard 9x19mm barrel rather than the standard .355")