Roughly .275 or .28 caliber. Take MM divided by 25.4 (mm/inch) and you get caliber in hundredths of an inch.
284
Of course not. .50 caliber weapons are.
The cartridge known as the 7mm-08 was derived from the .308 Win (7.62x51mm). The casing mouth is necked down from the original 7.62mm (.308") to 7mm (roughly .280").
No, 7mm and .284 caliber are not exactly the same, but they are closely related. The 7mm designation typically refers to the diameter of the bullet, which is 7mm (approximately 0.284 inches). The .284 caliber, on the other hand, specifically refers to the .284 Winchester cartridge, which uses a 7mm bullet. Therefore, while they refer to the same bullet diameter, they represent different contexts in ammunition terminology.
The caliber designation of 7mm-08 is considered a short action.
30/06 is one
It's basically impossible to answer the question as you asked it. Good for what?
An example of 7mm is the diameter of a typical pencil lead, which is often around this measurement. Additionally, 7mm can refer to the size of various small caliber ammunition, such as the 7mm Remington Magnum used in hunting rifles. In the context of photography, 7mm can also describe a focal length for certain wide-angle lenses.
If 7mm Magnum, it trumps the others.
The 30-06 shoots a bullet which is 7.62 mm in diameter, so the 30-06 is "bigger" in that sense. Several different weights of bullet are available in either caliber, so that's an undetermined variable. There are several different 7mm cartridges (7mm Mauser, 7mm Magnum, 7mm H&H, 7mm-08), so you have to be more specific when comparing ballistics.
probably 7mm or 8 mm
No because the barrel is made for that specific caliber and will not wear out the barrel.