ORIGINAL: cayugad
If the rifle has iron sights, pull the scope and try that load at 50 yards with out the scope. If it shoots a 2" group at that distance, then you might suspect the scope is no good. Or throw another scope on it and see if that makes a difference. Otherwise you are going to have to rework all the steps of what you do to the rifle and where you might have changed something.
While the scope can be the major problem, somehow I believe it is something else-an unclean gun. What gave me the first clue?? The dad-burn mn hangfire, that's what! Hangfires don't happen with clean flash channels!