When I did my own DSC1 about 12 years ago there was no mention of handloads or otherwise.
However, several friends of mine have did the DSC1 over the past five years or so and there was clear instructions in all cases that factory ammo only was to be used. How rigidly this is enforced is another matter, it is down to the range officer on the day. I went to one test day a few years ago and brought my rifle along to allow a friend to do the shooting test with a rifle he was familiar with. I had brought factory ammo along at that time, but there was no mention of it and the range officer was happy that we used my handloads.