Hi, Dave.
I own the SR40 and have shot 200 rounds of 155 Grain Lead Semi-Wad-Cutter bullets through the gun without a malfunction. I purchased the bullets through bulletsdirect.com. I loaded them over 5.0 Grains of Hodgdon's Universal Clays powder, in mixed once-fired brass, with a COL of 1.130", using Winchester small pistol primers.
I cleaned the gun last night and found significant leading in the barrel. However, after a couple of applications of Hopp's #9 and a couple of minutes of scrubbing with a brass brush, the barrel was clean. I did not notice any damage to the rifling. It is my understanding that the barrel has traditional rifling, not polygonal. Hope this helps.