Fallout 3/ New Vegas

Assault Rifle: Real life inspiration - HK G3; Evident in - receiver, magazine, forgrip, stock, sights; Changes - Caliber, metal coloration, size, magazine size

Chinese Assault Rifle - Real life inspiration - RPD, AK series, AN-94; Evident in - reciever (AK), Magazine (AK), Stock (AK/RPD), Muzzle Brake and sights (AN-94), Fore grip (RPD); Changes - caliber, proportions, mag size

Chinese Pistol - Real life inspiration - Mauser C96 .45 (obviously); Evident in - EVERYTHING; Changes - Caliber (.45 to 10mm), small proportions

.32 Pistol - Real life inspiration - Welby Mk 4; Evident in - reloading mechanism, grip, barrel; Changes - caliber, slight proportion changes

Light Machine Gun - Real Life inspiration - M60, FN Minimi/M249 ; Evident in - foregrip, carrying handle, heat shield, stock, magazine, muzzle brake, grip; Changes - Caliber (7.62 to 5.56), furniture (IRL - polymer, In-game - wooden),

Hunting Rifle: Inspiration - M40 series; Evident in - stock, bolt; Differences - manufacturing (the hunting rifle is clearly homemade), caliber (.32 vs .308/7.62)

Fallout 4

Combat rifle: Inspiration - BAR; Evident in - foregrip, stock, barrel; Differences - sights, magazine, receiver, caliber

Assault rifle: Inspiration - Lewis Gun; Evident in - barrel, stock, grip, size, sights; Differences - magazine, caliber, proportions, clasification (the Lewis Gun is an MG, this is called an assault rifle)

Sniper/Hunting rifle: Inspiration - M700, M40; Evident in - barrel, stock, body, magazine, bolt, caliber; Differences - not many