Joe,
There were many of the 3" Ordnance rifles converted in this manner to saluting guns. The 3' Ordnance rifle was a good field piece during the civil war as it was reliable with only one known instance of a gun exploding while in service. Contrast this with the Parrott rifle which fell out of favor with the gunners because of the frequent instances of gun failures and injuries to the gun crews. The ordnance rifle survived in active service the longest of any other type of civil war field piece. I believe some were used in the Spainish American war but not confirmed yet.
Ron