Green’s Dictionary of Slang

a prostitute; in cit. 1648 whore is implied.

1648		‘Mercurius Melancholicus’ Parliament Brought to Bed 4: [She] hath followed the Camp, & became an Amunition-W, and turn’d up her tayle to every lowsy [...] Rascall in the Army.
1681		W. Robertson Phraseologia Generalis 1320/2: A Ammunition whore; Scortum Castrense.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue n.p.: Ammunition Wives. Girls of the town, doxies Sea term.