Hello, Advocate!
Yes, I've done lots of cast bullet shooting with US and foreign military calibers including 6.5mm, 7x57, and 8x57, plus many of the old time blackpowder numbers.
In this country, the .30 calibers have found lots of favor with cast bullet shooters because of the great numbers of good .30 bullets around. Shooting costs can be reduced to a couple cents per round if you cast with free lead and use medium pistol powders like Unique.
I found the 7x57 to be particularly easy to load for and accuracy is often much better than with military ball. 1.5 to 2" groups are the norm even without load development.
One caution for everyone though: segregate your cast bullet fired cases from those you use for normal full-charge jacketed loads. There can be a problem from shoulder setback and consequent case separations if you don't.