Sheet2.Select 
    Sheet2.Range("K6").Select 
    For n = 1 To 52 
        Sheet2.Range(ActiveCell, ActiveCell.Offset(294, 7)).ClearContents 
        ActiveCell.Offset(, 9).Select 
    Next n
Range(ActiveCell, ActiveCell.Offset(294, 7)) = K6:R300
(9*52) + 11 = 479 [Offset = 9] [K = 11] [Last cleared Column = 486] [K = 11]

Eliminate 4 'dots' in loop = eliminate 208 operations 
With Sheet2
For Col = 11 to 479 Step 9 'Check the math
.Range(Cells(6, Col), Cells(300, Col+7)).ClearContents
Next Col
End With