Intended for use as training pieces, these guns were never planned to be used in combat again.  Severe wear on the barrels had reduced the range of the pieces from 10 miles to as little as 5! However, due to the shortage of usable ordnance at the outbreak of WWII, older guns such as the "Niobe's" were pressed back into service once again. 

At Ft.  Petrie the 6" guns continued in use until 1944 when they were replaced with the more modem 4" Twin Mounted Duplex guns.  These guns continued in service until the dismantling in 1956. 

Also in use at the fort was a Hotchkiss 6 pounder, which was used as a "stopping gun".  That is to say, the smaller gun was used to fire warning shots across the bows of suspicious vessels attempting to enter the port without permission.