Where and how big?  I don't use bullets with fins.  Fins from casting flash? Don't want fins in the grease grooves either.  I hate fins.

    Joe. 

Quote:
Fins decrease accuracy and are on the bullets because the mold halves are not fully closed.

So, squeeze the mold handles and hold the sprue hole up to a bright light.  If you see light at the bottom of mold:
* Hold mold handles and wiggle them up and down.  If there is play - tighten the handle bolt
* Check for burrs & remove them on the cavity using a Q Tip to check for & then a razor blade with a light scraping - repeat holding to light
* Check for lead on the inside of the mold sides - remove with solvent
* Still have light?  Put mold halves in a padded vice and squeeze them together  
* Still have light - contact the vendor
Good Luck
 

Quote:


How important is accuracy?

Obviously they're good for the 2 fouling shots before the match.  OR they're good for plinking and MAYBE good enough for minute-of-beer-can accuracy.

westerner wrote on Dec 7^th, 2013 at 6:07pm:


40-65 ought to do it.

I have one mold where the vent lines are a bit too deep and the pins are a bit too tight.

When my alloy is very hot it will start migrating into the vent lines.

To get this mold to work well:

1. Turn the heat down a bit
2. Tap the side of the mold with a rubber hammer to set the pins snug/tight before pouring a bullet
3. Reduce the time I hold the dipper against the sprue plate since the weight of the lead in the dipper helps drive the lead into the wide vent lines.

If I get fins on the nose I throw them back in the pot.
Light fins on the side of the bullet get shaved off by my resizing die. (Use sizing die the same diameter as the base of my bullet).

The vent lines start at the bullet bands so there are never any fins in the bullet grooves.

This isn't for the faint of heart.  But, it will cure a finning mold about 9 times out of 10, if it isn't caused by junk buildup or lead stuck between the halves.

After cleaning every spec of lead out of the mold and verifying there isn't a foreign object holding the halves of the mold apart, if you still see light between the halves, then you need to resort to more agressive techniques.

The first thing I do (after removing sprue plate and cleaning all foreign junk and lead out is:

Put the mold on my anvil with the parting line between the mold halves parallel to the anvil face.  Use a 2 pound or so hammer, and smack the mold with it, medium hard.  Check the mold and see if it fixed it.

Repeat, harder, if it didn't.  Don't beat on the mold repeatedly, just one blow and check.   

If that doesn't work, the second step is to look at the alignment pin holes and see if there's any obvious interference, and may have to file or grind just a hair off if there is.

If the alignment pins aren't doing the problem, see if the blocks are warped.  If they're hitting in one spot, you can sometimes lap a bit off of them with 400 grit wet/dry on a perfectly flat, polished surface (like table of your mill) and get them to fit better.  Be careful what you're doing, use indicating fluid or sharpie marker on the faces to make sure you know where you're removing material.  Do a bit, check, repeat.  Don't blindly just lap off material without knowing it's coming from the right area.  Re-assemble and check often, stop when you can't see light.

dave

What happened to namvet67?   

    Joe.