Problem with my casting

[Charlie Two Tracks]

I am making out of round boolits. In a .390 mold, I can have almost a thousandth smaller at the joint where the two halves meet. I also get this with a beagled mold. I can see that because the tape is on the inside of the mold. What do you think I am doing wrong? Like Chief Lone Waite said, I am endeavoring to persever. I am using WW with tin added but it seems to happen whatever alloy I use.

[lwknight]

OK , I'm confusing about the tape thing but what I think may be happening is shrinkage.
If its a multi-cavity mold, the area between cavities can be hotter than the sides.
The alloy on the sides will solidify faster than the area between cavities. Shrinkage will affect the softest portion of the casting.

Antimony will stop shrinkage and a sizer die will round the bullets.

[Bodine]

Almost sounds like you have a speck of lead on one of the mold halves, on a cold mold take and look with a magnifying glass and see if you find a little speck of lead that is not aloowing the mold to come all of the way together.

[prs]

Think about it for a long time and declare war on the pale faces.

Is this just one mould or several? Did Beagling reduce the error by the thickness of the shims, or did the error increase?

prs

[Charlie Two Tracks]

The error increased. On a beagled mold, it can be up to .002 difference. The molds are clean. The wider part of the boolit is opposite where it closes together.
lwknight, that sounds like what could be happening. The mold with the greatest variation is a two cavity brass mold. Maybe I should add some linotype? Would a hotter mold help? I pour at 720-750 most of the time.

[runfiverun]

think about what happens to steel/aluminum/brass when it gets hot.
it does that in every direction.
the greater radius of the half circle will of course expand the most.

[williamwaco]

What kind of mold is it?

Close it tightly, open the sprue plate and hold the base of the mold up to the light, look into the cavities and see if you can see light through the closure.

I am 99% sure the mold is not closing completely.


.

[Charlie Two Tracks]

Thanks runfiverun. that makes sense.

[MtGun44]

If the boolit is 0.001" out of round, and you think this is a significant problem, you kinda need
to reset your expectations. This is pretty much just fine and will work out in the sizing.

Round is overratted, really. I'd love to have perfectly round boolits fall from the mold, but
it is actually a fairly rare event. Doesn't hurt them for most purposes.

If I were casting for 300 yd match shooting in a rifle, I might get that picky. For pistol and
moderate range rifle, I'll be pretty impressed if you can make Mr. Target take notice.

Bill

[Charlie Two Tracks]

You're probably right MtGun44. lf I take a brass .359 mold and cast away, I get .358 at the seams and .359 at the radius. If I beagle, I can size the boolit down but on a flat based boolit, you can get a ridge protruding from the bottom of the boolit just a little. I really don't know if that is a big deal or not. I am trying to get a very soft round for my wife to shoot. It seems that on the lower powder loads, there is a better chance of leading.
MtGun44, that load you gave me for the LEE 158 RNFP with H-110 is fantastic. I have over 1,000 of them loaded and at least that many shot. At 100 yds I had 2 touching, 1 a 1/4 inch away and the others within two inches out of my GP-100. If I had a magnifying scope, I bet they would group all together. At 100 yds, the dot on my Red dot scope pretty well fills the bullseye of the target so it is kind of hard to see exactly where you are but that's quite all right. Thanks again.

[lwknight]

I'm with you on that Bill. Probably all boolits are less than exactly perfect.
I never gave it a lot of thought but upon reflection , every boolit I ever put through a sizer
showed imperfections in roundness by the width of the bands fluctuating slightly.
The sizer die works wonders.

[mdi]

.001" out of round? Near perfect. Do you know how small .001" is? No problems with those bullets, but when it gets over .010" then you have a problem...

[Charlie Two Tracks]

The problem is- if my mold throws a boolit at .358 on the radius and .357 at the seam of the mold, it will lead like crazy in one of my revolvers.

[runfiverun]

the only way to fix across the seams is to lap the mold.
this will help round things out too.
we deal in thousandths of an inch.

[MtGun44]

I tend to agree on the lapping. It will round things out and make it a bit bigger, so now the
sizer will give you a round boolit.

Glad you like the load. I have found that the Lee 358 158 RF is a superb design. The H110 load
does shoot very well for me in several different .357 mag pistols, too. I have actually not tried it
at 100 yds, but I should, I guess. I like that it doesn't need a GC, yet shoots really accurately
and no leading, even with hot loads.

Bill

[Charlie Two Tracks]

I'll give that a try. Thanks guys. It's getting real cold again around here so I should have time to get it lapped and do some casting before I want to go to the range again.

[Charlie Two Tracks]

Well, I got up this morning and started to lap the brass mold out with Barkeepers Friend. It is a two cavity mold and I used the screw method in the boolit and turned it by hand. I just used 4 boolits and you could see a little bit of brass on them after 20 revolutions. I just got done cleaning the mold up and casting some at 700 and 750 deg. . The 750 ones seemed to fill out better but I will try again after a bit. The 750 deg. boolits measured .360 at the radius and .3596 at the seam after going through the sizer. I'm thinking that is close enough for now. I will see if they shrink or not. The alloy I used was 16 lbs of WW and 1 lb of Linotype just because that's what was in the pot. Thanks guys. It was kind of spooky doing it but I didn't mess anything up and it seems to have improved the situation.

[runfiverun]

makes e'm fall out of the mold easier too.
i'm getting to the point that cleaning molds and polishing them is just a habit.
i have rejuvinated a few old molds this way too.
over time and use they tend to get a little mis-aligned and sloppy.