Bottom pour voides

[smylee grouch]

With the topic on melting pots and the use of bottom pour to cast, I,m wondering if when casting with that bottom pour causes more balls with voides as there is little or no puddle on the top of the sprue cutter for the extra lead needed during the cool shrink process. Would this be more noticeable when casting larger balls?

[Daryl]

When I used to cast using the bottom pour pot, I did not hold the sprue plate up against the nose of the pour spout.  Doing that, causes too many slivers of lead on the sides of the ball due to the vents. I held it slightly below and poured the lead into the hole and thus could shut off the pour at the right time to get a puddle on top of the sprue plate.
If the little feathers don't happen if you hold the sprue plate up against the pot, I think your lead is not hot enough.  At least my system of pouring the lead into the hole in the sprue plate gave me perfectly good consistent balls. It also worked with bullets, however I made better bullets with dipping after I disconnected the bottom pour system. I disconnected the bottom pour system due to
aggravation with leaks & dribbles.

[Scota4570]

I get a much higher percentage good bullets with bottom pour.  It depends on the mold and alloy if I use the pressure casting technique.  Some molds puts whiskers on the bullets if you do that.   If I was getting voids I would make a stop on the valve to slow the flow.  I would also increase the temperature.  I look for about five count for the sprue to harden.  IF the cavity is is liquid for a few seconds I would not expect to have voids. 

With very large balls, .990" I sometimes get shrinkage dents. I have not figured that one out. 

[Don Steele]

I use basically the same technique as Scota4570. I use a thermometer in my lead throughout the casting session. I maintain 800 deg. F. . There is ALWAYS have a "puddle" on top of the mold and I do the same short count before opening the blocks. There have been occasions when I have stopped the flow before the "puddle" had fully formed, leaving very little metal above the sprue plate. On those occasions I have definitely observed the formation of a tiny "dimple" in the metal as it cools. When that happens, those balls aren't kept. EVERYTHING I cast is weight graded. For the 40 cal RB's my acceptance standard is +/- 0.1 gn. and I get a very high acceptance rate. Well up in the 90% range.
Coupla other notes:
I discussed the LEE bottom pour pot that I'm using in the other thread. One thing I didn't mention in that thread is that I cast a variety of bullet alloys besides the "pure" lead for RB's. I only own one pot so periodically I'm called upon to empty the pot of whatever is in it into an ingot mold when I want to switch alloys. I take advantage of having the pot empty to dismantle the bottom pour assembly and thoroughly clean everything inside with steel wool and wire brushes (including one mounted in an electric drill) to remove any accumulated "Crud" and get everything back to bare metal. Drips/dribbles are not a problem for me. FWIW, I'm casting bullet weights up to 500 gns for BPCR and my .458 Winchester Magnum. Acceptance standard  for 500 gn  bullets is +/- 1.0 gn.. %. My acceptance rate on those isn't as good as what I get on the small RB's. I don't shoot enough of them to adjust my technique or change equipment.
Hope this helps.

[smylee grouch]

I don.t use the bottom pour any more because I would ge those voids and the pot would always drain and drip. I would always hold the mold up tight to the pot and got no or very little puddle. That might have been one of my problems but I switched back to dipping and have been a happy caster since.

[Scota4570]

" the pot would always drain and drip."

I never understood this.  The valve rod has a screw driver slot to seat it if crud is causing a leak.  Also, do not fill it with dirty scrap lead and expect it to not leak a little.  Use clean lead. 

When I cast I use gang molds when I can.  I try to do about 500 balls/bullets in a session.  That does not happen dipping a single cavity mold.  I am very results oriented.  I see casting as a cost saving thing, I do not particularly enjoy it.

With a big bottom pour pot you can run two gang molds at once because you can over heat a single gang mold.  That is lots of balls real fast.   

I did not mention that I always leave a puddle, even when pressure casting.  I fill the cavity, then back off and make a puddle.  IF you don't have a puddle you will get a shrinkage void.  Having a puddle makes it easier to make the sprue release from the sprue plate.   IF you try to cast through a niblet of lead in the sprue plate you will likely get a bad bullet.   

[EC121]

My pot is 20yrs old and corroded.  The screwsdriver slot doesn't always do it.  I put a Lyman ingot mold under the spout and let it drip.  Doesn't drip that much.  I can pick up the drips with pliers and put them back in the pot.

[Daryl]

Find a method, bottom pouring or dipping, that works for you and stick with it.