sentry duty vs sentry go

sentry duty and sentry go both are nouns.

Word	Noun	Adjective	Verb	Adverb
sentry duty	Yes	No	No	No
sentry go	Yes	No	No	No

As nouns, sentry duty and sentry go are synonyms defined as:

Other synonyms of sentry duty include guard, guard duty.

sentry duty (noun)	sentry go (noun)
the duty of serving as a sentry	the duty of serving as a sentry