bullet loads

Question
Dear Rod:
I write mystery/suspense novels.  I have a scene in a current project where a victim is shot by two handguns - a 38 special and a 9mm.
My question is in examining the bullets later, what would be the determining evidence between the two bullets? diameter?  grain?
I'm an ex San Franciscso cop, but truthfully, never could figure out what the bullet grain really meant.
Any help you could provide would be greatly appreciated.
Jerry Kennealy

Answer
Jerry,

The determining factor in my mind would be the bullet diameter, a difference of a mere .002". A 9mm shoots a slug that is .355" while the .38 shoots a slug with a diameter of .357". Here's a source that may help you with other aspects:

http://www.chuckhawks.com/compared_9x19_38Spec.htm

I hope that helps! -Rod-

Followup: Sorry I forgot about your question about grains. Grains is simply a more accurate way of determining the weight of an object and is used in determing the weight of cartridge cases, powders, as well as bullets. Using grams would be too inaccurate, ie, there are 308.6 grains in 20 grams or 15.43 grains per gram. The bullet weight in grains has a lot to do with how much energy is imparted into an object and in a spy novel setting, a heavy bullet, with an appropriate powder load would be subsonic. -Rod-