are ya cleaning the bore between shots? this makes a difference, especially if its rifled. we always swab between shots when sighting in.
the barrel shrinks and expands with temp changes...a few shots can make it drift.
3 years old is 3 years old...they dont care if it stayed in a box for 2 and a half years. maybe just off the shelf with a valid receipt will work though.
i had a deer hunter scope one time... lol they make things interesting.
my burris scopes are dead accurate, i wont try another til they let me down.