The result of your conversion between grain/quart [US] and kiloton/cubic mile [UK] appears here
To convert between Grain/quart [US] and Kiloton/cubic Mile [UK] you have to do the following:
First divide ((0.45359237/16)*(192/175)/480)/(0.0037854118/4) / ((0.45359237*2240)*1000)/(((0.0037854118/231)*1728*27)*5451776000) = 280.89723149
Then multiply the amount of Grain/quart [US] you want to convert to Kiloton/cubic Mile [UK], use the chart below to guide you.
Symbol:
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Symbol: kt/mi³
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