Warped moulds?

[Ken Hansgen, 11094]

I've noticed when I run some of my bullets thru the lubrisizer, I get a little lube squeezing past the front of the bullet at one spot, where a sizing mark does not appear. Why are these moulds irregular? I have often warmed them by dipping a corner into the molten lead--has that warped them? I'm suspecting this contributes to inaccuracy.

[Southron Sr.]

Dear Ken:

Yes, your mould could be warped. Now, I don't know IF dipping a corner of a mould in a pot of molten lead to pre-heat the mould will warp a set of blocks-but I don't recommend doing it. I have found the best way to pre-heat a mould IF you use an electric pot is to simply place the blocks on the lip of the lead pot when you turn it on. That way, the blocks heat slowly and evenly.

Another technique I have used in the past is to EVENLY heat the blocks with a propane torch, starting with the cavity. Care must be taken to NOT oveheat the blocks when using a propane torch.

Are you using a RCBS of Lyman mould? These moulds are made using the "cherry" method and sometimes they come from the factory "out of round," i.e., oval shaped. This discrepency is sometimes hard to spot with the naked eye. That is why I have such a high regard for lathe bored moulds-they come off the machine absoutely "round."

I would suggest replacing your mould. Whatever you decide, GOOD LUCK!

[Ken Hansgen, 11094]

Brannen, I have found this problem in both a Rapine and a Lee mould. Who makes the "bored" moulds?

[Pat in Virginia]

Ken,

It is possible the problem lies with the lubrisizer. I have an RCBS lubrisizer and when I use the set screw to tighten the top punch it takes the top punch off-center. To rectify the problem I just don't tighten the top punch set screw any more.

Try that and see if your problem is still there. It's a cheap fix. It's also worth knowing that the lubrisizer can actually introduce out-of-round bullet inconsistencies. It's easy to check for: 1) you can get out your calipers and take measurements; 2) you can give the bullet a quarter twist after sizing and send it down again. If you feel resistence similar to what you did the first time you sent the bullet down, you have the problem. Just don't tighten the top punch set screw and see what happens.


Pat in Virginia

[Paul Lampman 263V]

I also had an issue with Rapine molds a long while back. Seems that the blocks were assembled off center from each other causing a seemingly out of round condition. Had one set replaced twice and never got a perfect mold. Decided to look elsewhere.

[Paul Lampman 263V]

I also had an issue with Rapine molds a long while back. Seems that the blocks were assembled off center from each other causing a seemingly out of round condition. Had one set replaced twice and never got a perfect mold. Decided to look elsewhere.

[Paul Lampman 263V]

Sorry about the double post, sometimes I loose patience with this antique. Anyway check out the bullet with a micrometer or dial caliper to check roundness out of the mold. If it's not round then it will be sized with one side lube grooves deeper than the other, allowing lube to squeeze by.

[Ken Hansgen, 11094]

I tried Pat's suggestion on my Lyman Lubriser--that wasn't it. Tomorrow I'll mike the bullets. Thanks, KenH

[DAVE FRANCE]

In addition to the molds being made imperfectly, the bullets will come out of the mold out of round because as the mold cools the bullet does not solidify evenly in the mold. I confirmed this with a couple N-SSA members who make molds for castings (but not bullets).

The molds can't cool evenly because the distance from the mold cavity to the outside of the mold varies. I think that as the lead solidifies the coolest part of the melt, takes metal from nearby melt that is hotter. I know this is true for very large castings. Large castings have several sprues (a columns of molten metal) that feed metal to the large casting as it solidifies.

I have two very accurate custom made molds, and they are better, but they won't give perfect bullets. It is really asking a lot to expect a bullet to come out of the mold perfectly round to within one thousandth of an inch.

It does help to get good castings by keeping the melted lead a consistent temperature. It took me 25 years in the N-SSA to realize that using two pots would help. I never put cold lead into the pot. I take lead from one pot that is used to melt the cold ingots, and put the molten lead into the pot I pour from.

David

David

[Southron Sr.]

Dear Ken:

You would have to check with Ray Rapine, but I have a suspicion he uses cherries, but I am not sure.

As for Lee, they advertise that they lathe bore their moulds.

Your problem might be using aluminum moulds. Aluminum is a very poor choice to use to make moulds out of; but everyone makes their moulds out of aluminum because it is so cheap to buy in bar stock form compared to brass.

I only make my moulds out of BRASS. If you ever get used to using a good brass mould, you will never go back to aluminum. Brass is 1000% better!

Your Friend,
Brannen