[iraiam]

45 auto and 45 ACP are the same thing, ACP stands for Automatic Colt Pistol.

.357 Magnum, This is a magnum with a bullet diameter of 0.357". This one confuses many people, a .38 special also has a .357 diameter bullet but a shorter case than the 357 magnum. (357 magnum is a 38 special with a longer cartdridge case and thus more powder)

357 SIG is basically a .40 caliber pistol case which is necked down to hold a .357 diameter bullet.

380 usually refers to a 380 ACP, 380 Auto, 9mm short, or 9 X 17, other names liekly exist for this caliber. I believe the outside diameter of the case is right about 0.380" where the bullet is seated into it.

.38 and .380, I don't have enough information to answer this question, but again the 0.380" is the diameter of the round.

There are a few different cartridges that carry 38 with them such as 38 special, 38 auto (different than 380 auto), 38 super auto.

I would suggest typing each of the calibers you want to know about into Wikipedia, the information there seems to be accurate.

I hope this helps, it can get confusing.