Buffalo, to lap, you need to get a centered machine screw into an already cast bullet to serve as a shank. I do this in a lathe and would hate to have to try any other method. That's the hard part.
To enlarge a mould, I coat the bullet with fine valve grinding compound, chuck the shank in a drill press, set the press to a slow speed, grab the bullet with the mould, and turn the press on. 30 seconds or so is plenty. There is a certain feel for it you need to avoid making your mould eggshaped, but you are making a very small change and a little off won't hurt anything.
Before I ever enlarged one, I had polished a half dozen. Same routine, but I use a paste of Old Dutch cleanser and water instead of the grinding compound. That's an extremely mild abrasive, but it's enough to get the tiny burs that make bullets hang up in a mould. Because it is so mild, it takes a very long time to remove significant metal so it's pretty safe. 30 seconds gets the burrs, but hardly affects the rest of the mould at all.
Well, The above description by Leftoverdj is a very good description of how it "should be done", and I'm sure it's much more precise than what I have to say, so I'll just throw in two other methods that have "worked" for me.
Remove the head of a Dry Wall Screw, using the "shank" only, open the sprue cutter of your mould and insert the screw with the sharp point up. Pour your mould as full as you can w/o making a mess on top of the mould......while using pliers, try to keep the screw as centered, and horizontal as possible to the center of the mould.
Remove all the excess / overflow lead from the bullet you have just cast with the screw in in it.
Drill the end of a 1/2" --3/4" dowel rod, that has been cut to about a 6" length, and screw the screw, that is now anchored in the bullet into the dowel.
I use LBT Bore Lap, but any fine abrasion such, as valve grinding compound, Bon-Ami, Old Dutch, or whatever, will work.
I then coat the bullet with mineral oil, put the "paste" of scouring powder on the bullet. I then close the mould around the bullet with the paste, put it in lightly in the vise, and turn / spin the dowel, back an forth, in the palm of my hands.....This can take 3/4/5 minutes of turning by hand, sometimes more, sometimes less...you never know, so go slow and measure often.
Clean the mould, using alcohol, or break cleaner, to remove your mess. Cast a bullet, and when cool measure it.
Keep this up until you get just what you want.
You can get the same results by using a handheld rechargeable screwdriver on the screw by, leaving the screw head in place, and using the screw "starter" that comes with the drill. And, it is much faster than the hand turned dowel. ( I prefer a screw starter with the outside sleeve that slips completely over the screw)
Of the two methods described, I prefer using the wooden dowel, it seems I can control it much better.
Respectfully, Russ
