I also purchased a SBE a couple of years ago. I have every choke tube combo even a Pure Gold .
These choke tubes were used with every single buckshot load Winnchester makes, copperplated and non-copperplated . You might need to do what I did , buy a Browning Gold ! I still have my SBE,
but only use it for slugs . $1200.00 slug gun Ouch!