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tking308
08-19-2015, 10:47 PM
I'm getting good fill out but often more than half of what I'm casting ends up with pin holes in the bases. This is a gas check boolit so idk if it matters but it's ugly.
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lobowolf761
08-19-2015, 10:52 PM
It looks to me that you need to have a larger sprue. When you are casting keep pouring a bit longer than you have been to help insure a complete cavity fill. A bigger sprue helps that happen.

depoloni
08-19-2015, 10:55 PM
IDK, based on the details given, if you might not already be doing so...

My initial impression is to suggest you fill the (if not over-fill) the sprue cavities more. Seems like I've run into this problem in the past on occasion due to alloy shrinkage in the mold when not giving enough melt on top to back-fill during shrinkage.

Others may have similar, or different/better advice naturally. Hope this helps.

country gent
08-19-2015, 10:59 PM
The pin holes may be coming from the bullets cooling before gases are fully gone. What temp is the metal? What alloy is the metal? is the mould fully up to temp? Are the vent lines clean and clear? how tight loose is the sprue plate. SOmetimes lightly stoning the inside top edges of the blocks at a 45* angle for .003-.005 down helps provide a vent line right at the top of the blocks letting gasses air flow out better. Have temp of alloy around 700*- 725* and preheat mould to around 350*-400*. You want the sprue to take 3-5 seconds to solidify ( actually solidify not see the "frost" come over). This allows time for air and gasses to work out. You should see the sprue "dimple" as it cools showing it is sucking metal in to fill voids as it cools.

tking308
08-19-2015, 11:03 PM
The pin holes may be coming from the bullets cooling before gases are fully gone. What temp is the metal? What alloy is the metal? is the mould fully up to temp? Are the vent lines clean and clear? how tight loose is the sprue plate. SOmetimes lightly stoning the inside top edges of the blocks at a 45* angle for .003-.005 down helps provide a vent line right at the top of the blocks letting gasses air flow out better. Have temp of alloy around 700*- 725* and preheat mould to around 350*-400*. You want the sprue to take 3-5 seconds to solidify ( actually solidify not see the "frost" come over). This allows time for air and gasses to work out. You should see the sprue "dimple" as it cools showing it is sucking metal in to fill voids as it cools.


This sounds very likely too me. I've been waiting until it frosts over but not alwats until it dimples.

OnHoPr
08-20-2015, 02:57 AM
Well, I never seen holes like that on the outside of the sprue. But, I will guess that maybe it is a vent problem. It might also be the angle of the pour. It could be that you are hesitant with the pour at the top when the cavity is about full or that you may have a little jiggle with your hands. Pour a good stream all the way up to the top and make a good sprue. I can tell you for sure IMO that the two boolits on the bottom of the right pic that you opened the sprue plate to early. The middle boolit looks like you cut the stream before the mold got filled. The 2nd from the top looks like you didn't fill completely or had a hesitant jiggle when you stopped the pour, but you waited long enough to cut the sprue. Same way with the top, but you cut it too soon. What does a profile pic show of the boolits. Are these boolits on the big side like 44 cal and 270 gr or bigger. If you are running bigger boolits on a good run with a hot mold just before frosting even though the sprue looks completely set doesn't mean the inside of the boolit has cooled enough. For example, when I get in a groove casting the Lee 501 440 gr I might wait another 5 seconds or so (dadedadumdideda) after the sprue cools before cutting it.

10x
08-20-2015, 08:27 AM
1) raise your alloy temp 50 degrees F
2) leave as large a sprue as possible on the sprue plate. It should take at least to the count of 7 or 8 for the sprue to go solid, and 3 to 5 seconds after that you break the sprue off.
See if the voids disappear.

RobS
08-20-2015, 09:26 AM
Trapped air. Often times a change in the way a person pours the lead into the mold will fix this especially if using a bottom pour pot. One who directs the lead flow straight into the sprue plate hole creates a more turbulent flow of lead into the mold cavity so rather try and hit the side of the sprue hole with the lead stream creating a swirl effect into the cavity. As been mentioned the mold sprue plate being too cold can also be cooling the base before the lead can be drawn into the mold so creating a larger sprue puddle on top may help. Possibly a small increase in alloy temp could help too.

mozeppa
08-20-2015, 09:28 AM
could be contaminated lead.

Wayne Smith
08-20-2015, 12:22 PM
In my experience pinholes in the center of the boolit are caused by the shrinking of the alloy in the mold as it initially cools and not having enough liquid lead in the sprue to draw down and fill the shrink hole. This can be caused by inadequate sprue, by a cool sprue plate that cases the sprue to solidify before the boolit cools, or by interupting the sprue prior to the draw down. If your mold is working well you can look at the sprue puddle and see the draw down before it hardens.

williamwaco
08-20-2015, 01:47 PM
Wayne + 1

And if the sprue puddle is small enough, you will see the pin hole in the sprue before you cut it
off

bruce381
08-22-2015, 02:06 AM
when i get this its from either too small sprue and or to fast to drop it.
going bigger sprue and longer time for sprue to cool solves it.

JonB_in_Glencoe
08-22-2015, 09:08 PM
I'm getting good fill out but often more than half of what I'm casting ends up with pin holes in the bases. This is a gas check boolit so idk if it matters but it's ugly.
147075147076
IT will matter with Rifle boolits.

Add more heat, as in casting faster, and a larger sprue puddle.
and BTW, unless that's a bevel base boolit mold, I wouldn't call that good fillout.

AND THIS \/

The pin holes may be coming from the bullets cooling before gases are fully gone. What temp is the metal? What alloy is the metal? is the mould fully up to temp? Are the vent lines clean and clear? how tight loose is the sprue plate. SOmetimes lightly stoning the inside top edges of the blocks at a 45* angle for .003-.005 down helps provide a vent line right at the top of the blocks letting gasses air flow out better. Have temp of alloy around 700*- 725* and preheat mould to around 350*-400*. You want the sprue to take 3-5 seconds to solidify ( actually solidify not see the "frost" come over). This allows time for air and gasses to work out. You should see the sprue "dimple" as it cools showing it is sucking metal in to fill voids as it cools.

my 2¢
Jon

Ole Joe Clarke
08-22-2015, 10:04 PM
Sprue plate could be to tight. Should be loose enough to swing from it's on weight.

243winxb
08-22-2015, 10:12 PM
Dirty alloy. Sprue loose. More heat. Don't pressure cast. Let the alloy drop into the hole.

OnHoPr
08-27-2015, 02:38 PM
Just for the heck of it are you using a Lee dipper or small dipper? Your dipper might not have enough lead in it to cast a boolit that size. That is why you may be running out of pour steam at the end of the pour causing your symptoms.

Ola
08-27-2015, 03:04 PM
The only time I had that was with Lee bottom pour when I was little careless.. The stream of lead was so strong it was splashing out of the cavity too. I just slowed the stream down a bit and that solved it.

My theory is that when it is "splashing" the air gets trapped.

HATCH
08-27-2015, 03:06 PM
In my experience pinholes in the center of the boolit are caused by the shrinking of the alloy in the mold as it initially cools and not having enough liquid lead in the sprue to draw down and fill the shrink hole. This can be caused by inadequate sprue, by a cool sprue plate that cases the sprue to solidify before the boolit cools, or by interupting the sprue prior to the draw down. If your mold is working well you can look at the sprue puddle and see the draw down before it hardens.

this is your problem.