the "cut the sprue-move the sprue plate back so the hole is not over the bullet base but the sprue plate is over the bullet base-whack the sprue plate to flatten the lump" method, which I invented.
After casting and opening the sprue plate, close the sprue plate such that the plate and not the hole is over the bump, and give the top of the sprue plate a good whack with the yellow plastic mallet. This will mash the bump down and make it go away.
Bullet bases will be flat.
joe b.

I hate to admit it, but I face butt of in a lathe in a 3jaw chuck, all same length n weight. Works for me...

OK first never hit your mould. Don't whack it on top don't hit it to shear the sprue, Never hit your mould!
Now First the edges of the hole in your sprue plate should be sharp. If they are not sharpen them one of two ways. First way use a countersink and carefully take out material until the edge is sharp. Back the plate with a piece of hard wood or soft aluminum. Most commercial plates are soft steel and punched out on a punch press. Now lap the side that mates with the mould until it is flat. 
  The other way is to find a drill that is a .0001 or two over the size of the sprue hole and drill it out, then lap the plate. Don't open it up to much as this can cause problems with casting. 
Now that the sprue hole is sharp you can cut the sprue cleanly. I use a spring washer (not a lock washer) on all my moulds. Screw it down tight and back off about a 1/4 turn. Now use your gloved hand to push the sprue plate open. If you don't use a glove use a hammer handle to push it off. Don't hit your mould, it never hit you.
Once the hole is sharp and you can shear off the sprue it should cut cleanly and not have those bumps.

40 Rod

I agree with 40_Rod and KAF.

  But to sort of answer Hank45's question. I tried that idea of squaring the base of the bullet up many years ago and as far as I could tell it didn't improve accuracy at all.

  Of course if the cavity is not square to the top of the mould it would probably help, but in that case I would send it back to the maker for another one, or my money back.

Pete

When the world and I were young I tried bumping bullets. I had a set of swage dies made to my specs of what the nose and base should be. I then cast the bullets and lubed them then ran them through the swage die to just give them a bump. After two years of doing this I decided that it had little is any effect. My attitude now is to buy a good mould from a good mould maker cast them lube them and shoot them. The more that you fool with the bullet the more chance that you are going to screw it up. 

40 Rod

Hank45, You are looking for the  PRECISION BULLET EDGER I went thru a few years of BLACK POWDER CARTRIDGE NEWS and found adds for it from 2003 thru 2005. The web site (You need to Login or Register to view media files and links) is dead. There is a phone number 315-823-2395.  607 Cramer Rd., Little Falls N.Y. 13365 I did not try the number and it would seem they may not make it anylonger?
I knew I had seen it someplace, just had to look around. Hope this helps.
Tom

Quote:

Please tell us why not. Share your experience as a mold hitter, that caused you to become converted to the correct path. Or you just parroting silly opinion?
joe b.