weaponry vs arms

weaponry and arms both are nouns.

Word	Noun	Adjective	Verb	Adverb
weaponry	Yes	No	No	No
arms	Yes	No	No	No

As nouns, weaponry and arms are synonyms defined as:

Other synonyms of weaponry include implements of war, munition, weapons system.

weaponry (noun)	arms (noun)
weapons considered collectively	weapons considered collectively
	the official symbols of a family, state, etc.