Caliber is the measure of th internal diameter of the barrel in inches- a .30 caliber gun fires a bullet that is about 30/100ths of an inch across. European guns are usually measured in millimeters- a 9mm fires a 9mm diameter bullet. Bigger number equals bigger bullet. GAUGE is an older term used to measure the internal diameter of a shotgun barrel. It came from the number of round lead balls that fit the barrel that add up to one pound. So 20 balls in 20 gauge weigh one pond, 12 balls in 12 g weigh one pound, etc. SMALLER the gauge, bigger the barrel. The .410 shotgun is the exception- that is really .410 caliber.
Caliber is the size designation for rifle and handgun bullets. Guage is the size designation for shotgun rounds.
@ .05 inches
20 gauge is larger
22 is a rimfire, 222 is a centerfire.
They are the same; just said in different order.
the 40 cal is a little bigger then the 357
The size of the bore.
A pressure gauge indicates actual pressure and a differential pressure gauge indicates the difference in pressure.
about .03 inches
5.62 is bigger
Size of the bore.
Glock is a brand. 9mm is a caliber size. So, there is no difference between a 9mm glock and a 9mm of another brand as far as caliber size.