I shot a kestrel from Huntertown at a fun shoot the other day. Full auto indoors. It seemed to cut the noise a lot but I still had hearing pro on of course. Was impressed.

From what I have read a lot of manufacturers sell stainless cans. Seems like most claim 17-4. Anybody know if the actual threads are this composition of stainless?

The majority of the time the threads will be of the same composition as the can itself. Usually it is easier and more cost efficient in the manufacturing process. If you have a stainless barrell and are worried about galling, use some anti seize and you will be fine. (Really you only need to worry about galling if the materials are the same- i.e. both are 316L or 440L, etc. If they are two different grades of stainless, galling is not an issue.)