gun chamber vs firing chamber

gun chamber and firing chamber both are nouns.

Word	Noun	Adjective	Verb	Adverb
gun chamber	Yes	No	No	No
firing chamber	Yes	No	No	No

As nouns, gun chamber and firing chamber are synonyms defined as:

gun chamber and firing chamber: chamber that is the part of a gun that receives the charge

gun chamber (noun)	firing chamber (noun)
chamber that is the part of a gun that receives the charge	chamber that is the part of a gun that receives the charge