Well, I checked out the eBay inconel 625. Straight bits are hard to come by,
but bends are easy to find. I found a 14"x2.25x.049 double 20 degree bend
for $20.00. The asymmetry of the blast tube in a square tube tangential
muffler application might just be an advantage. Item No. 300295559215
Check it out.

C Smith