Yes, it is, they are both 6mm. The .20 gram bbs are for use in higher quilty guns, likve over $100. They are more acurate, but dont shoot as fast.
I do not know of a production airsoft gun that shoots bbs of those dimentions but it doesnt mean its not out there As you probably know, most common is 6mm, and some airsoft guns, specifically some revolvers, shoot 8mm bb's, but I have never heard of a 7mm bb or a gun that shoots it.
do you mean a marble that shoots BB's or can you shoot marbles out a gun. It does not matter since you can't do either of them.
well most c02 guns shoot faster with the .20 gram so with the .12 gram it will probably shoot at around 410-420
If you use airsoft gun in public place or pretend it's a real gun - yes, you can be shoot. Do not use airsoft guns in public places!
it depends what your shooting at. But if you just shoot one at a wall or something like that nothing happends.
No, it shoots 3 at once.
A gun that cocks back automatically after you shoot.
Hmmm. Interesting question. A bb is propelled by an air piston - cylinder design out of the barrel of an airsoft rifle. Due to the sound of the mechanism, it does sound like the gun "shoots", however, there is no explosive or gunpowder involved in the process. It all depends on how you interpret "shoot".
No company owns the rights to airsoft. Airsoft is just a general term for an air rifle that shoots plastic pellets. BB rifles also shoot plastic pellets, but a true airsoft gun uses a more complicated firing system then that of BB guns.
Depends on the laws
YES
no, it doesn't