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Slims · 10-26-2008, 02:56 PM

Ok, here is a quick and dirty breakdown:

You have basically two things that matter with the caliber itself. First, is the size of the round, and second is how much 'oomph' it has.

These bullets are all the same diameter, but have been given different names because other aspects of the cartridges are different:
for auto loading pistols: 9mm Parabellum (normal 9mm round), 9mm makarov, .380 ACP and 38 super.
For revolvers: .38 Special and .357 Magnum

There are others, but these are the main ones. They all fire comprable bullets, but the shapes of the cartridges, as well as how much power they have are all different. For instance, there is very little difference between a .38 special and a .357 magnum. In fact you can safely fire .38 special rounds in a .357 revolver, and it is done quite commonly for practice as the ammunition is cheaper and has less recoil. This is because the original .38 Special cartridge was black powder, and thus needed a lot of volume in the cartridge to fit enough powder to produce moderate chamber pressures. Since the old guns that were designed for those original, low pressure cartridges are still around, manufacturers cannot safely boost the pressure through the roof to increase velocity without risking accidents. So the solution was to create a slightly different cartridge, the .357 which would only chamber in new manufactured pistols which could tolerate the higher pressures.

With the 9mm and the .380 Auto, they are basically the same round, but the .380 auto is more compact and less powerful, lending itself to use in smaller weapons.

Cal. and mm are used seemingly randomly in the gun world, though I believe it originally had to do with where the round was first put into production.

Typically, the most preferred handgun rounds for self defense are these: 9mm, .40 S&W, .45 ACP for auto pistols, and for revolvers .357 Magnum is the gold standard.

10-26-2008, 02:56 PM	#2 (permalink)
Slims Eccentric insomniac Location: North Carolina	Ok, here is a quick and dirty breakdown: You have basically two things that matter with the caliber itself. First, is the size of the round, and second is how much 'oomph' it has. These bullets are all the same diameter, but have been given different names because other aspects of the cartridges are different: for auto loading pistols: 9mm Parabellum (normal 9mm round), 9mm makarov, .380 ACP and 38 super. For revolvers: .38 Special and .357 Magnum There are others, but these are the main ones. They all fire comprable bullets, but the shapes of the cartridges, as well as how much power they have are all different. For instance, there is very little difference between a .38 special and a .357 magnum. In fact you can safely fire .38 special rounds in a .357 revolver, and it is done quite commonly for practice as the ammunition is cheaper and has less recoil. This is because the original .38 Special cartridge was black powder, and thus needed a lot of volume in the cartridge to fit enough powder to produce moderate chamber pressures. Since the old guns that were designed for those original, low pressure cartridges are still around, manufacturers cannot safely boost the pressure through the roof to increase velocity without risking accidents. So the solution was to create a slightly different cartridge, the .357 which would only chamber in new manufactured pistols which could tolerate the higher pressures. With the 9mm and the .380 Auto, they are basically the same round, but the .380 auto is more compact and less powerful, lending itself to use in smaller weapons. Cal. and mm are used seemingly randomly in the gun world, though I believe it originally had to do with where the round was first put into production. Typically, the most preferred handgun rounds for self defense are these: 9mm, .40 S&W, .45 ACP for auto pistols, and for revolvers .357 Magnum is the gold standard. __________________ "Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery." - Winston Churchill "All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find that it was vanity: but the dreamers of the day are dangerous men, for they may act out their dream with open eyes, to make it possible." Seven Pillars of Wisdom, T.E. Lawrence Last edited by Slims; 10-26-2008 at 02:59 PM..