punch bag vs punching bag

punch bag and punching bag both are nouns.

Word	Noun	Adjective	Verb	Adverb
punch bag	Yes	No	No	No
punching bag	Yes	No	No	No

As nouns, punch bag and punching bag are synonyms defined as:

punch bag and punching bag: an inflated ball or bag that is suspended and punched for training in boxing

Other synonyms of punch bag include punchball, punching ball.

punch bag (noun)	punching bag (noun)
an inflated ball or bag that is suspended and punched for training in boxing	an inflated ball or bag that is suspended and punched for training in boxing
	a person on whom another person vents their anger