"One clever and awesome weapon the rebels improvised to compensate for their shortage of artillery shells was the thunder barrel. The device was fashioned from large hogshead barrels filled with powder and fuses passed through the bungholes. Soldiers lit the fuses and rolled the barrels down the hills into the Yankee trenches. They made similar rolling bombs out of Union naval shells that had failed to explode, recycling the North's own weapons against them.
[The Most Glorious Fourth: Vicksburg and Gettysburg, July 4, 1863, p. 118]

[http://books.google.com/books?id=tle5pvItKfQC&pg=PA117&lpg=PA117&dq=%22Thunder-Barrel%22&source=web&ots=Aoa0uxWDZA&sig=n_ljSMiqsmV8d3dGnx53cIcvWLA&hl=en&sa=X&oi=book_result&resnum=5&ct=result#PPA118,M1]