Green’s Dictionary of Slang

1. (US) beans.

1908		Dly Missoulian (MT) 18 May 4/3: A ‘bunch of bullets’ means a plate of beans.
1914		G.D. Chase ‘Navy Sl.’ in DN IV: ii 150: commissary bullets, n. Beans.
1927		Danville (VA) Bee 27 May 3/1: The U.S. Navy has a language or a ‘slanguage’ all its own. For instance [...] beans are ‘bullets’.
1931		Irwin Amer. Tramp and Und. Sl. 40: bullets.–Beans, often served so poorly cooked they are as hard and as indigestible as their namesake.
1944		P. Kendall Dict. Service Sl. n.p.: pass the bullets . . . beans.
1960, 1975		Wentworth & Flexner DAS.
1962		Ragen & Finston World’s Toughest Prison 792: bullets – Beans.

2. peas.

1959		I. & P. Opie Lore and Lang. of Schoolchildren (1977) 183: Peas are ‘bullets’ or ‘cannon balls’.
1960, 1975		Wentworth & Flexner DAS.