machine gunner vs serviceman

machine gunner and serviceman both are nouns.

Word	Noun	Adjective	Verb	Adverb
machine gunner	Yes	No	No	No
serviceman	Yes	No	No	No

As nouns, serviceman is a hypernym of machine gunner; that is, serviceman is a word with a broader meaning than machine gunner:

machine gunner: a serviceman in the artillery
serviceman: someone who serves in the armed forces; a member of a military force

Other hypernyms of machine gunner include man, military man, military personnel.

machine gunner (noun)	serviceman (noun)
a serviceman in the artillery	someone who serves in the armed forces; a member of a military force