A very general range is .17 to .50.
There are over 2000 different cartridges (and calibers) for different firearms.
Among the smallest cartridges is the 2.7mm Kolibri centerfire pistol cartridge (about .09 caliber)- among the largest, 2 bore paradox (about 1.800 caliber)
Books with multiple hundreds of pages have been written to answer this question. There is no way to answer it here.
There are many different types of guns! Shot guns, rifles, hand guns, pistols, even paint guns and air soft guns. Then with each type there are different callibers, which is the size of the bullet that is shot through it. the higher the number the bigger the calliber therefore the bigger the bullet and generally the bigger the gun.
It depends on which gun. Different guns assemble in different ways.
You Cant
hand gun, long gun.
No they are very different things.
The receiver is the frame of the gun. When a gun is marked with a serial number, it is stamped on the receiver. It will be a different part depending on the type of gun.
The gun weighs MUCH more than the bullet.
no, because they believe that same gun powder can use in different types of guns and that will also cheap
Start by taking the gun to a gunsmith. There are different firing pins for different guns.
A BB gun is an Air Gun. Now if you are asking is a BB gun better than an "Air Soft" gun that is different. As for better, well it all depends on what you want it for. A BB gun will do more damage than an Air Soft gun. But that doesn't make it better. basically an air gun has hollow pellets to a bb gun a bb gun has metal balls so they are basically the same gun but with different types of bullets
You need to define the term gun license. In most of the US there is no license to own a gun. Some states require a license to carry a gun. others to carry a gun concealed. There is also a license to make or sell guns. All are different and have different procedures.