Shotguns are refered to by "gauge" not "caliber". It should be marked on the barrel.
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.)
You need a gunsmith
5x4.5in or 5x114.3mm
Depends on the caliber.
no
A bolt is a screw I think.
Try egunparts
17 Remington.
Caliber, where made, bolt
100-300
wal-mart