shire town vs county town

shire town and county town both are nouns.

Word	Noun	Adjective	Verb	Adverb
shire town	Yes	No	No	No
county town	Yes	No	No	No

As nouns, shire town and county town are synonyms defined as:

shire town and county town: the town or city that is the seat of government for a county

shire town (noun)	county town (noun)
the town or city that is the seat of government for a county	the town or city that is the seat of government for a county