I posted about these a long time ago, wondering what the materials were after seeing "stainless steel" on Major malfunctions website which now says stainless steel and inconel. Never got any answers, and finally did.
The baffles and tube are 625 inconel, and the girdle 304 Stainless steel. So yeah for all intents and purposes it has the strongest combination of materials of any silencer on the market (at high temperature), I believe.
The 625 has about twice the tensile and yield at room temperature of 316.
625 has the yield strength at 1800F of 316L at 1200F, and the tensile of 316 at 1600F, when the 625 is at 1800F
Other manufacturers use 718 which has better properties- for baffles, but apparently KAC is the only manufacturer to use Inconel tubing.
I don't really want to dig up the old post, but would like to let people know I had found an answer in case they were wondering what it was.