Hal9000, thanks for the links to the anodizing and electroplating, they were enlightening. You core with the pressed baffles sounds interesting, but I am afraid the welds might fail under stress after a while if they are not against the tube wall. But I'm not sure.
My attempt at pressing sheet metal with dies was very rudimentary, I used a 6inch vise to apply pressure and I attempted to heat the metal with a propane torch. I am not surprised that I failed.
I watched a program where a guy was making aluminum pot lids by spinning a piece of aluminum sheet metal on some sort of lathe and pressing it with a round tool of some sort to mold it into a concave shape. I would like to be able to do that to make the basic shape then trim it down to the exact size required to fit snug in the tube.
I think some engine mufflers use a design that is not linear. The engineer can make the gases go any direction he wants without worrying about a projectile passing through. Anything that wears away (wipes and mesh) is a poor choise for a gun silencer unless you are able to replace it requently. The ATF allows wipe replacement, but only after destroying the ones in use.
Ranb