Rifles are mostly 5.56 and handguns are 9mm. There are other calibers that are used, but those are the most common.
barrett M82
It is a self loading handgun that fires a bullet nominally 0.45 inches in diameter. Which there are numerous DIFFERENT .45 caliber pistols, the best known may be the 1911A1. Initially adopted by the US military in 1911, it served as the main US military handgun until recent years.
ABOUT .69 to .75 caliber. These were smoothbore muskets.
US
Not in the current U.S. military. the most common handgun caliber currently is the 9mm.
30/06. A 30 caliber cartridge adoped in 1906 for US military use.
No reference for a savillion rifle. If you mean civilian, same as for a military rifle- it will depend on the caliber and barrel. Military rifles in the US are made by civilian companies.
It denotes a type of 30 caliber ammunition adopted by the Military in 1906.
If military issue, is not refinished, between $300 and $500 US.
age of the military 1911 is based on serial number................
The 6.8 mm SPC is a new cartridge being considered by the US military. About the same length as the current 5.56 cartridge used in the M16 rifle, it has a fatter bullet- about .277 caliber.
If your question is can citizens of the US own a .45 cal handgun, the answer is yes. MOST of the US does not require a permit to own a firearm, and even the areas that DO require permits do not ban the .45. In some countries private citizens may not own a handgun in a military caliber, but the US does not follow that practice.