I tried for a while for a drilling and had no luck. I ended up buying some newer 7x57 R and fireforming.
One thing I found is that the 7x57 wouldn't fit in my chamber since it was so tight. There is a very slight difference. I simply used an 8x57 reamer in till it just polished the breach end of the chamber and it worked. Only removed a couple of thousandths of the rear 1/2" of the chamber, which was unnoticeable. I have tried in a couple of other guns since and those chambers readily worked without reaming. The original one was a high quality Berlin made gun known for exacting finish and it apparently had a minimum chamber.