Ultra-long-range match bullets for the big boomers are made of lathed mono-metal. It doesn't matter to me, but I am guessing that mono-metal target bullets can be lathed in a way that allows them to travel down the bore with less resistance and less deformation, thus producing more consistent BC over the flight of the bullet. I don't think this matters for bench rest, but it likely does at a mile and beyond.
Do they still machine driving bands into them? That feature is nearly impossible to make on a conventional jacketed bullet.
Monos also solve the problem of bullet blowup from driving long, high BC bullets fast.
