Those are post cold war "fads", and are equipment for the 21st century military; see US Army small arms (21st century) websites.
M147.62mm Rifle
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You sight-in a M2 Browning with the M2 Browning itself.
Your Answer: M14 7.62mm Rifle
ABOUT .69 to .75 caliber. These were smoothbore muskets.
50 caliber
The typical rifle bullet was .303 inch caliber. The same round was used in most of the light machine guns.
Austria, Australia, New Zealand, and Ireland use it as their standard issue rifle. Several other military forces issue it to select units.
".303 British" is usually used to denote a caliber, as opposed to a specific firearm. Perhaps the most famous rifle in that caliber was the SMLE, which is the abbreviation for Short, Magazine, Lee Enfield. There were several marks and models of British military rifles that originated under that designation, all in that caliber. They were made from prior to WW I, and continued through the Commonwealth nations (and former Commonwealth nations) into about the 1960s. So, yes, the caliber .303 British and the Enfield name are linked- but Enfield is not the full name of the rifles and carbines. Run a Wikipedia search on SMLE for some more reading.
Some law enforcement agencies have used the .270 as a sharpshooter's weapon, but it was never military issue.
Impossible to answer without more information.
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.
The Universal company did make a civilian version of the M1 Carbine. Not all of the Universals use the same parts as the military issue M1 carbine. Please note this is caliber .30 Carbine, and not the 30-06 caliber of the M1 Garand rifle.
barrett M82
M14 was standard issue military rifle before m16.
No. The SMG is a pistol caliber machine gun, such as 9mm, .45 ACP, etc. The AK is an automatic rifle. You may see them referred to as an assault rifle.
7.62 mm (or 30 caliber) and 5.56 mm (or 223 caliber) are common rifle cartridges. Pistols, machine guns, and artillery will of course be different from these.
British: Lee-Enfield Bolt-Action rifle, Sten Sub-Machine Gun, Bren Light Machine gun, Vickers .303 Machine gun. American: M1 Garand Semi-automatic rifle, M1903 Springfield Bolt-action Rifle, Thompson Sub-Machine Gun, BAR (Browning Automatic Rifle), M1897 Trenchgun shotgun, M1919 .30 Caliber Light Machine gun, .50 Caliber M2 Browning Heavy Machine Gun, Bazooka. German: Karabiner 98K Bolt-action rifle, Gehrwehr 43 Semi-Automatic rifle, STG44 Assault rifle, FG42 Battle rifle, MP40 Sub-Machine gun, MG34 Medium Machine gun, MG42 Medium Machine Gun, Panzershreck. (I may have missed a few. Sorry.)
QBB-95 is a Chinese light machine gun. QBZ-95 is a Chinese assault rifle.
Bolt action military rifle, most commonly in caliber .303 British.
ABOUT .69 to .75 caliber. These were smoothbore muskets.