Well, you got me curious; the article I read goes back to 2001 and isn't easy to find. Carpenter is describing both 465 in the cylinder, and a special 15-5 in the barrel in their applications notes. I'll see if I can find the original article.
I did have my .480 SRH at the Hog Hunt one year, and a few guys shot it. That load was 24gr of Lil'Gun under 355gr hard cast. It was running 1300 fps, but was not as consistent as I'd like. Assuming Enforcer ever becomes available again I'd like to try it with those bullets.
