JB for Leementing

[mattd]

I'm casting out of round 44 bullets with my 310g lee mold. .427-.432 on a single bullet. And they are all frosted with the lee pot turned darn near the lowest setting, cool down time between pours, and a clean mold. Time to leement. Opening the vent lines will hopefully help with the frosting. But I have some significant lapping to do to even out my circumference. .432 would be perfect btw. Is JB bore bright course enough? Or would there be a better compound to start with?

[RickinTN]

I've done one mold, and it was the same mold you are working with. My specs on bullets were about the same as well. The first "trick" is to go slowly. I didn't have any luck with the approximate grit you are speaking of. I think it would be pretty good to polish a mold, but won't do much cutting. I purchased some valve lapping compound at the local auto parts store and it worked very well. I used a system very similar to what most folks recommend however it altered it somewhat. Instead of using a screw through the center (approximate center anyway) which was long enough to go all the way through the bullet and take a chance on it going through I bought self-tapping screws that would bottom on the bottom of the bullet without going all the way through. With this set up I could turn the bullets in the cavities without worry of the screw damaging the mold. I also could turn it with a socket and a ratchet or a power drill. I was in a way lucky in that the gas check shank on my mold was undersize. I lapped it as well, and when it approached the proper diameter I "turned" the shank on subsequent bullet such that they made no contact. This method can also be used to have the bullets only lap that portion of the mold where needed.
Good Luck with your project,
Rick

[Iron Mike Golf]

Matt, you may want to consider returning that mold. Is it a 2 cavity one? Lapping a mold may correct out of round. My (and others') experience is lapping will increase the diameter in all orientations.

If you do lap it, use an abrasive made to cut metal. 240 to 320 grit lapping compound should work good. As you lap it and you pour boolits to check your progress, go ahead and size them after you mike them. You want to make them big enough so the sizing die can make them both the right size and round.

.005 difference is an awful lot and I'd really think about returning the mold.

[Larry Gibson]

If the bullets are all frosted the problem is probably one of casting too hot, especially if using straight COWWs. If that's the case then reduce the heat of the alloy to 725 degrees and add 2% tin to the COWWs. That Lee mould should cast very good bullets then and probably will be close to .432 w/o leementing or lapping the mould.

You may have to reset the knob on the Lee pot to turn it down more. Also get the alloy into the mould as quick as possible from the spout and pour a generous sprue to the point of run off. Adjust your casting tempo so the bullets are not frosted.

Larry Gibson

[montana_charlie]

Opening the vent lines will hopefully help with the frosting.
??? ... where did you pick that up?

CM

[detox]

Sounds like the alignment pins have receeded. If mould gets too hot pins will slip causing mould halves not to line up. The new two pin Lee moulds are not very durable and care must be taken during casting. Cast at cooler temps (under 700) and do not slam mould haves together. Lee menting will not fix.

[mattd]

If the bullets are all frosted the problem is probably one of casting too hot, especially if using straight COWWs.

That's sure what I thought. Not WW, but close. 5lbs #9 mag shot, 5lbs pure, 2% pewter.


You may have to reset the knob on the Lee pot to turn it down more. Also get the alloy into the mould as quick as possible from the spout and pour a generous sprue to the point of run off. Adjust your casting tempo so the bullets are not frosted.

I had it set between 1 and 2 while trying to eliminate the frosting. If I threw a pinch of sprue cuttings in the whole thing started to solidify. So probably close to the lower temp limits?

I adjusted my tempo, I dabbed the mold on a wet cloth, I took a break and cast some 40s. Still frosty. Increasing the pour speed out of the spout helped fill out, but not frosting.

[mattd]

??? ... where did you pick that up?

CM

Over at castpics.....
http://www.castpics.net/subsite2/MoldMods/Fixing%20Lee%20Molds.pdf

[mattd]

Sounds like the alignment pins have receeded. If mould gets too hot pins will slip causing mould halves not to line up. The new two pin Lee moulds are not very durable and care must be taken during casting. Cast at cooler temps (under 700) and do not slam mould haves together. Lee menting will not fix.

This could something. What is the fix if this happened. Close the mold in a vice and try to gently tap them back in place?

[montana_charlie]

Opening the vent lines will hopefully help with the frosting.
??? ... where did you pick that up?
Over at castpics.....
http://www.castpics.net/subsite2/MoldMods/Fixing%20Lee%20Molds.pdf
Go read it again.
There is plenty of detail on improving the venting on a mould, but the goal is to improve fillout.
The word 'frost' is not even used in the article.

CM

[mattd]

Guess i'm making the assumption that if there is a known potential issue w the venting, and im getting frosting while casting at low temps and taking steps to keep the mold temps lowish, then that might solve the problem. But you know what they say bout assuming. Its a secondary issue to the size issue anyway and looking closer at the mold the vent lines are very small and not something i'll mess w at this point

[Larry Gibson]

Your pewter (can be 85 - 90% tin with the balance antimony, copper or lead) may be adding more antimony or some copper to the alloy. The magnum shot runs around 5% antimony and cutting that with the lead drops it to around 2 1/2%. Suggest you get some 50/50 solder and add that instead of the pewter to a batch. If you pick up a 1 lb bar of 50/50 solder then add 6 1/2 oz of that bar to 5 lbs shot and 4 lb 10 oz of lead. Or if you can pick up some pure tin then add 3.2 oz to the shot and lead. If that works then you'll know the problem was the unkown composition of the pewter.

Larry Gibson

[detox]

This could something. What is the fix if this happened. Close the mold in a vice and try to gently tap them back in place?

RCBS makes good moulds.

[mattd]

Well I lapped one cavity, as well as put a set screw on the sprue screw, moved the alignment pins to improve alignment, and tightened the handles pivot screw. Both cavities are producing bullets that are ~.003 out of round.....so better then before. The one I lapped is .432-.435.

Got a lee .430 sizer on the way, and will hone it out to .431. If I can get the bullets thru it easy enuf, and they shoot well, I'll lap the other cavity, and after lots and lots of work I'll have something functional.

[dromia]

What has happened to the frosting?

[mattd]

Still a little frosty. The first couple come out not frosted, and are much less wrinkled then I was getting at the start of previous casts. But after two or three they settle into the frost. I'm running the lee 20 lbs pot so close to minimum that a couple sprues back in the pot and it solidifies, and in the 5 minutes of waiting for it to melt again it cools enuf to get non frosted for another 2 or 3. Casted a bunch of lee 175g TC 40s out of the same pot and they are good to go.