What I find interesting that back in the 1700's in older fortifications which had layers of defense
your first class guns were in the fort proper the 2nd class on the outer wall and
the third would be placed out beyond that, the third class guns could be 30 or more
years old, You will find Spanish artillery built in the 18th Century that had in the mid 1800's
had been rifled, I am wondering if there are reports of it still in use during the Spanish American war....
there is a photo in the current artilleryman that shows a period photo of American troops with a captured
Spanish copy of a french rifled mountain gun that was still in use.
it would appear that a system for retiring guns didn't come about until the
mid 1800's now it's down to a science, the military tests and tests to discover the limit
of the arms in use weather it be a M16 or a 155mm one weapon system they keep trying
to replace and just won't go away is the M2 Browning, there are guns that were built in WWII
that are still in the inventory. in 2002 I was at a Penn. National guard armory that still had some of the
older 105's one Breach ring I saw had a WWII date, the barrel was probably replaced a couple of times since
it was originally built but was still in secondary service.