I have anecdotal information to relay on this subject.
I chatted with a Hevi-Shot rep at Pheasant Fest yesterday.
According to this gentleman, the shot in the Classics Doubles load is softer than the shot their other loads.
He said that it was very much comparable to Bismuth. I asked if it was comparable to TM and he said yes,
but it did not use plastic as a binder.
According to the Hevi-Shot gentleman, any gun that you would have shot Bismuth through, you could shoot
HSCD through and not need to worry about barrel damage (that is if the gun is not too tightly choked).
FYI—I also asked about their Pheasant load and I understood that the shot in this load is as dense as lead
but not as dense as the shot in their duck and goose loads, I did not ask him about shot hardness for the
pheasant load. Sorry, I'm not an engineer, or even a physics expert. I could have asked better questions.
Not definitive info here, take this for what it's worth.
I was satisfied enough with the conversation that I now have no qualms about feeding both the
Pheasant and the Classic Doubles loads to my Fabarm Beta (not even close to a classic).
Jim