I'm getting some lead feathering around the base of my gas-check bullets in .358 and .452. Mountain Molds brand, brass, It's just enough where I have to touch it up with a file in order to instal the gas check. The sprue plates seem to be plenty tight.
Thanks,
Jeff

May be running a little too hot (brass molds are nice about heating up fast). Hot mold, good alloy, will often get little "feathers" (or "whiskers" as the lead flows into vent lines). MAy be using too much pressure...bottom pour...or too big a "puddle" when dip-pouring.

Hold the mold up to a strong light and take a look at that plate. Have seen some that if you tighten down too hard, it cocks the plate up, actually increasing the gap between plate and mold blocks. Have also run across some with a burr around the plate screw hole (put there by tapping the hole?), and "tight" was just tight against this raised burr.

Check too if you have any lead smeared across the bottom of the sprue plate. This will cause the sprue plate to ride against the lead deposited on the bottom of the sprue plate, and thus the sprue plate, rather than sitting flush on the top of the mold blocks, has a gap because of the built up lead smear, and will cause the base flashing that you describe.

God Bless,

Thanks guys.
I think I have some of all those problems. Too hot, too large of puddle, lead smear on plate.

What is the best way to remove the smear? I'm tempted to use some #400 wet/dry paper on a flat surface and move the plate on it in a circular pattern to maintain flatness.

Jeff

Jeff,

Take the sprue plate off your mold, and toss it into your hot lead pot for a couple of minutes, then fish it out of the lead pot with a pair of pliers (be gentle with the pliers, don't want to damage the surfaces of the sprue plate), and wipe the lead off the sprue plate with a pair of rough leather work gloves! It'll simply wipe off with the leather gloves, and you'll be back in business! It's that easy.

Let us know what you find,

God Bless,

Jeff, casting too hot will cause you to have the lead smear on the bottom of your sprue plate, but sometimes running hot is necessary for good bullets with a given mold and/or alloy. To avoid the buildup, try using a coating of DriSlide lubricant on the underside of the sprue plate, it will do wonders to prevent just such lead build-up, and it positively stops galling of the sprue plate against the tops of the mold blocks, especially under the hold-down screw.

DriSlide is an industrial lubricant primarily used in the plastic injection molding industry. I use it exclusively for a mold lubricant, and have it for sale as well if you can't find it in your location... email me if you're interested. I'm not trying to sell you something, really, I'm just trying to help you avert a common problem.

God Bless,