double lines

[semtav]

I am getting double parting lines on one of my good custom molds. Not always, but too often .
They bullets aren't dropping right out, and I have to give it a couple good wacks.
It almost appears that it is coming out a little , then making another parting line.
I see it quite often at the base, but occasionally it goes clear to the nose.

Any Ideas what I'm doing to cause it?
20-1 alloy is what I'm using.
535 gr .459 cal+
775 deg approx temp

[HeavyMetal]

It sounds like your mold is sticking a little bit when you open it up.

If you have to "diddle" with it a bit to open you'll get that second parting line.

Suggest you take a magnifying glass and look for a burr on both the parting line of the mold and around the alignment holes and pins.

If you don't find anything don't worry about it. It could also be the fact that the handles are not quite set up for the mold.

Next time you cast fill the mold, cut the sprue, and, before you open the mold, put your thumb on that part of the mold closest to the handle hinge point and right on the line seperating the two havles.

Hopefully you'll wear gloves, now with your thumb in position push on the blocks and open the mold at the same time.

Usually this lets the mold pop open and the bolit falls right into the palm of my hand. It will take a little practise to get the sequence down pat but this may be your best answer to avoid those double parting lines.

[montana_charlie]

Any Ideas what I'm doing to cause it?Being a custom mould, you shouldn't find any burrs that cause the bullet to stick, but the advice to look for them is good.
If that isn't the problem, you may just be in too much of a hurry.

If you wait five seconds for the sprue to solidify, twenty more seconds to cut the sprue, and open the blocks five seconds after that...the bullet should have had time to contract enough to simply fall out.

In other words, a forty-second cycle time, with the bullet in the mould for thirty seconds, seems to work well.

CM

[BABore]

Your relaxing your grip on the handles when you wack the sprue plate, or when you wack the handle pivot. I can make this happen on most any mold if I loosen my grip.

[semtav]

OK,
thanks for the ideas, I'm probably doing all of above, so I'll work a lttle more on technique and patience next time,
Brian

[geargnasher]

That happens to me on moulds that have to be beaten. The boolit might come partway out of the cavity right when it gets smacked and the edge of the cavity digs in to the boolit as it falls out. Try lightly lapping the cavities to polish any burrs.

Gear