newbie here - inquiry about flux core welding

[ElectricSpecter]

I'm new here and new to welding. This is my first post, so sorry if I sound clueless. I got a Lincoln MIG welder from Home Depot or Lowe's about a year ago and have been using it with flux core wire to weld mild steel. Im learning a lot but still have a long way to go. Right now im only using flux core since i cant get tanks for MIG.

Here's my question: I bought a 304 stainless steel muffler and i think my truck's exhaust pipe is 409 stainless steel. Can I weld these together with flux core?? I have looked for stainless steel flux core wire but cant find any. Some friends who TIG weld said to use 309 wire for different metals, but I can't find that in flux core either. Is this doable and if so what wire do I need? If its not possible my friend can TIG weld it for me but i rather do it myself to learn. He's new to welding too and knows TIG but not much about flux core or MIG. I don't care how the welds look just that they hold up and dont rust or break.

 

[IamMckenzy]

welding 304 to 409 with flux core might work but isn't ideal. 309 wire is what you'd use for dissimilar metals, but it's hard to find in flux core. If you can, mig with gas would be better. If not, your friend's tig welding could save you the trouble.