Ok, this is a dumb question to those who know and understand the subject because I don't. On a cold hammer forged barrel, does the steel have to be chrome-moly or could you use 416R? Or something other stainless?
The composition of the "cromoly" steel is usually different for hammer forging vs button/cut rifling. The processes are vastly different, so the material properties steel has for button/cut rifling may not be what you look for when hammer forging
Stainless is known for being malleable. I don't see why it couldn't be hammer forged. Hammer forging is the cheap option for mass producing barrels. Cheap being the operative word here and also my guess as to why stainless is not used for hammer forged barrels.