Yes, 2400 seems to do that, in my experience. With my supply of 2400, I reached that point at about 19 grains, but my powder is pretty old so that you reached it at 17.5 does not surprise. Incidentally, you and I both ended up in the mid-1300 range. In my case, I was using the H&G 220 gr Keith bullet (nr. 258, I think?) and a 6-inch late 70s Model 57.