Gun

arma de fogo

(portable, short weapon, for hand use)

canhão

(military: cannon with relatively long barrel, operating with relatively low angle of fire, and having a high muzzle velocity)

fuzil

(less portable, long weapon)

obus

(military: cannon with tube length 30 calibers or more)

pistola

(portable, short weapon, for hand use)

rifle

(less portable, long weapon)

acelerar

(speed something up)