All of his earlier shell guns had been cast solid , then had the bore drilled out -- the traditional way to make artillery .
The navy 's demand for 15 - inch guns to defeat the new Confederate ironclads placed Dahlgren in a dilemma .
All of Dahlgren 's earlier shell guns had been cast solid , then had the bore drilled out -- the traditional way to make artillery .
The navy 's demand for 15 - inch guns to defeat the new Confederate ironclads placed Dahlgren in a dilemma .