A couple of years ago I looked into the possibility of swageing my bullets from cold lead, I think the company that made the equipment to do this was Corbin in the US. I realised from day one that casting a perfect lead bullet is nearly impossible because of various factors, such as invisible voids, plus other variables caused by temperature variations in the lead and the mould. The main reason I didn't pursue this idea was the cost of the equipment which was over a grand US, and the fact that lead wire of a suitable diameter was not available here to make the slugs from, especially if you wanted a mix like 20-1.
Any way all this experimenting keeps my brain working, hopefully.
Mike.

1+ on Corbin sizing dies..these fit in loading press  and size nose first.  I have a Ballard A-1 Mid-Range in .40-63 everllasting.  This was designed for paper patch in that it has no throat..rifling comes right to chamber end.  The largest bullet that can be seated in case and chamber is .001 or .002 over bore dia.  I have used Ideal 406150 cast soft and seated with only base band in case with excellent accuracy.  Bullet  shows only very light rifling marks when pushed thru bore.  Wanting to try a heaver bullet, Lyman 403173 came to mind...but was undersize.  So a quick and dirty swage die was made up using a Lyman .406 sizing die, a nose punch turned up for a ring fit in die, and a base plug.  Nose punch drilled out oversize foe epoxy impression of bullet.  1 whack with rawhide mallet brings body to .406.  Thinking to go even larger for a .408 bore, bullet nose was deformed.  I have not tried these yet, but they should shoot.  Strickly black in this one, and should bump to groove dia.