I would suggest going back to your customer and asking them to define the shot requirement. Maybe they could inform you of the media specification. 550 size is normally associated with cast steel shot which is magnetic. There is stainless cut wire, glass and ceramic peening media.
Hi, Donhan, You may well have solved this problem but just for the record, you could try using Guysons Spherically Conditioned Stainless Steel Cut Wire Shot. it comes in many sizes, the closest to 550 would probably be made from the Ø1.5mm cut wire.
Hello Tom, thank you for your advice. My teammates have similar project and they were looking for a solution. Tomorrow when I live my house I will stop by at their office and will let them know. Thank once again
Donhan, To be cautious you should ask your customer to be more specific about the non-magnetic shot. It is possible they did not want a metallic shot in order to prevent ferrous contamination or rust. They may have thought they would get ceramic beads or glass beads with their request.