Problem Child.

[USSR]

Did a little casting this weekend with my MP molds. First, I've got a new Lyman Mag 25 casting furnace that is a big improvement over my Lee Drip-O-Matic. However, it requires me to gravity feed the mold because the top of the sprue plate pivot bolt interferes with the bottom of the furnace housing on the cavity closest to me. And, my MP 358-429 simply refuses to fill out properly when gravity feeding the molten lead into it. My MP 454-423 mold on the other hand is just fine. I tried loosening up the sprue plate bolt on the MP 358-429 mold and that helped a little, but it still won't fill out properly. Any ideas? Thanks.

Don

[Ben]

Sounds like a venting problem.

[Toymaker]

Could be oil in the pores of the mold. Boil it for 20 minutes, the wash it with alcohol while it's still warm.

But, most likely - as Ben says - it's a venting problem. Rub the vent channels with a wood toothpick, round ones work best.

[sutherpride59]

Did you preheat the mold on a hot plate? I cant get good boolits unless I get mine to about 300 degrees first.

[Beagle333]

Are you making sure that the lead stream is centering on the hole and not hitting the sprue plate and rolling off into the hole? Sometimes just that little of a delay in getting it to the nose of the mold will cause poor fillout. Also, do you have the pot set up to pour at maximum flow? I have seen slow/small lead streams also take too long to fill the mold. I like to flood that thing fast.
And lastly, have you tried a different filling order? Some of my molds (and I can't explain this) fillout better when filled from nearest cavity to end and some do better filling the opposite order. I have suspicions as to why, but it doesn't matter, I just do what it wants. 8-)
Good luck!

[10x]

Also you should have a large sprue to force lead into the mold, and to keep the sprue plate hot.
You may want to raise your alloy temp 10 or 20 degrees as well.
Venting problems - maybe
once you get it sorted out you will get good bullets