The result of your conversion between gigajoule and grain/cubic foot appears here
To convert between Gigajoule and Grain/cubic Foot you have to do the following:
First divide 1.0e+09 / ((0.45359237/16)*(192/175)/480)/((0.0037854118/231)*1728) = 436995725880.08514404
Then multiply the amount of Gigajoule you want to convert to Grain/cubic Foot, use the chart below to guide you.
Symbol: GJ
No description
Symbol: gr/ft³
No description