The message
from Grunff contains these words:

I suspect your drill is simply getting clogged and so is unable to cut
any further in. The trick with soft materials, especially something like
lead, is a very slow drill speed, and I mean really slow. Drill a little
way in, and lift up to allow swarf removal. Repeat a few times until
you're at the required depth.

And experiment with the angle of the cutting edge of the drill. Too
sharp may cause problems if it's trying to remove too much material at a
time.

--
Skipweasel
Pay no attention to that man behind the curtain.