What is the difference between a 38 and a 380 handgun?

Answer 1

.002 inches in bullet diameter. While the bullet is a bit smaller as noted in the answer above the handguns that use these cartridges are very different. A .38 is usually a .38 special, which because of it's rimmed case is predominatley used in revolvers. A .380 is a rimless cartridge used in easily concealed blowback automatic handguns. The .38 special revolver has about 20% more stopping power than the .380 automatic. Both are considered adequate but not powerful personal defense arms.

Answer 2

38 is a rim fire for revolvers, 380 is smooth case for semiautomatic pistols.