Help with iron mold

[will52100]

So far nearly all my casting has been with aluminum molds, with one RCBS iron hollow base mould. Now I get great bullets with aluminum, but with the new Lyman mould it's been an up-hill battle. I can get decent bullets, but there's a high rejection rate, where with my aluminum moulds I have very few bad ones. What am I doing wrong?

Thanks

[oneokie]

What defects do these boolits have that cause you to reject them?

[will52100]

Mainly incomplete fill out and wrinkles. I've tried differant heats and mould hotter and cooler. Seems to resopnd better to laddle filling and lightly tapping on mould while still liquid helps. I'm using straight WW with just a bit of tin added. It's a 45 cal. RNFP 350 grain rifle bullet, I don't have this much trouble with my 500 grain 45-70 loads.

If I get good nose definition and fill out the base won't fill properly, if the base does rite a lot of times theres wrinkles or frosting on one side of the nose.

[oneokie]

Have you cleaned the mould to remove all traces of oil? Have you used any lube on the sprue plate and/or pins since cleaning the mould? Could be oil contamination.
Sounds more like the mould is cooling off between pours. Have you noticed which block is causing the defects? If it is the half with the sprue plate, are you cooling the plate to speed up the cooling of the sprue?
Some of the more knowledgeable casters will have more ideas of what to do.

[will52100]

It varies on which side the problems occure on. It's agrivating to say the least, I don't have this problem with any other mould, including a bunch of cheap Lee moulds that produce better bullets than this.

I've cleaned with soap and watter, acetone, got it up to heat and used graphite spray lube on the spure plate, that didn't help, so I tried the Bull Plate lube, that helped the spure release, but not the bullet formation. I've smoked it untill I'm about ready to realy smoke it with the torch till it's a pile of molten iron. Actualy I'm thinking of giving lee a hollar and seeing if they can make a custom mould in this style, maybe with slightly bigger lube groves. (it's for a 76 carbine and will be shot almoust exclusively with black powder)

[oneokie]

Suggest you clean the mould again. Use the search function here to look for posts on mould prep. Break the edges of the blocks at the top. Could be that you are getting air trapped under the sprue plate.

[will52100]

I'll give it anouther cleaning and see what happens. A thought that occures to me is that the sprue plate seemed loose and I tightened it slightly. Maybe that is cutting the airflow down. It also seems that the vent lines in the block are space a little far apart. I'll tinker with it till I get it figured out.

[runfiverun]

run a razor blade down the vents.
you also didn't say how you were pouring your boolits? bottom pour, force feeding?
ladle pour?
some times the larger molds just liked to be filled fast.
i have a 7mm and a 308 mold identical to each other but the 7mm likes to have the lead dribbled in and the 308 likes it to be lined right up with the sprue holes and shot in there.