Gun

cañón

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

charpe

(portable, short weapon, for hand use)

escopeta

(less portable, long weapon)

fusil

(less portable, long weapon)

obús

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

pistola

(portable, short weapon, for hand use)

rifle

(less portable, long weapon)

disparar

(speed something up)