??? On Drive Band Fillout .

[GP100man]

The drive bands are`nt filled out , is this caused by the mold gettin to hot in places ???

I think it is ,just wanna confirm it , this mold with the long slender 30 caliber holes warms up qwik !!!!

These 2 boolits were cast at the same time & the GCed 1 is good enuff for me to call perfect!!!

I run a 10# pot with a Lyman thermometer at 725f-750f.

Isotope alloy which is 2-3% tin already !!! & bhn 10.5, Ive run these thru the 06 with good succes with 16gr of 2400 , thinkin of turnin up the pressure a notch.

http://i746.photobucket.com/albums/xx110/GP100man/102_0417.jpg

[runfiverun]

look closer, the entire boolit ain't filled out.
the bottom is what i look for also, grey/galvanized coloration, square everywhere.
it's a pouring issue, either where/how fast or a venting issue.

[Will]

looks like the mould may be too cool or not enough pressure from the pour. IMHO a bottom pour will fill out better than a dipper. The diffrence in weight might give an accuracy problem. If I get a bad fill I just toss them back and pour again at a cost of $0.

[mooman76]

Could be ay of the above mentioned. Can't be the mould is too hot in places or you would have frosting. Bottom pour or top?

[lwknight]

I don't know what to say. I figure that you know what you're doing.
Maybe you are just pouring too slow.

[cabezaverde]

I have this same problem with a couple of my molds. Will be watching the replies.

[Doby45]

I would say it is a venting issue in the cavity that is not filling out well.

[HeavyMetal]

Try dipping the sprue plate every other round.

My experience with un filled bases is the plate is to cold all the time.

Figured this out when I started casting HP's and I went from as 40% scrap rate to about 1/2%

[GP100man]

Is it possible that where the stream is hittin the mold it gets it too hot & wants to vaporize some part of the lead or an impurity ??? But Ive never found any signs of trash or impuritys ????

The other side of that boolit is perfect almost & the boolit beside it was poured from a 10# lee bottom pour a second later.& I put generous sprue pour on em to keep the plate hot.

I just can`t get the idea of a ht spot out of my mind !!!!!

[lwknight]

What baffles me is that if it were a venting problem, the lack of band fill out would not likely be completely symetric because no one can hold the mold exactly still and perfectly level. Besides that , the lead stream is swirling to boot.

Searching my memory , it is possible that the mold is too cold
and you have enough tin that it will not show the typical wrinkles.
I just don't see the definitive tattle tail.

Has that cavity been making good boolits in the past? And is it intermittent or always the same thing in its respective cavity? I had something like that when I tried some mold release and was impatient and did not let it dry overnight.

Edit: I think I want to lean to the cold mold theory.

[buck1]

Its one of 3 things. your alloy,temp,or venting. as some boolits are filling out. I am going to say temp. try casting at a faster pace untill you have to wait for sprues to harden and you get a frosted boolit. if they are then good at that stage, you wernt hot enugh. If not look at vents.

[Mal Paso]

More heat! When I started with a Lee bottom pour I had spout freezes which tells me the spout cools the lead. You might try putting a cup under the spout and run a boolit's worth of lead into it before pouring the first boolit. The casting temperature that really matters is the one inside the mold after the lead has made it's trip from the pot. The thermometer tells you the temp you're starting with.

[cbrick]

Just a SWAG but I have a few iron molds that will do that and this might possibly could be maybe the same. It's not normally that severe but does look quite similar.

Once the mold is up to temp and it's casting well if I then get to casting a little too fast the mold begins to get too hot first in a spot or two, usually in the bottom of a lube groove. I call the effect "heat shrink" for the manner the melt starts to avoid this spot. Ok, that's another SWAG and my pet nick name but if I slow up a little the problem goes away, if I don't slow up it gets worse and kinda looks like yours. My SWAG is that the density of the iron could be a little different in that spot and gets hotter first. Nope, no scientific evidence to back that up, it's simply my SWAG for what happens with my molds.

Just a little something for the gray matter to chew on.

Rick

[leftiye]

Some alloys do that. My wheelweights, and 50/50 refuse to give me sharp corners unless I'm right at the edge of frosting. No nice and shiny with that alloy. I've got boolits that I cast thirty years ago that are so pretty that they piff me off.

Agree with cbrick too. If the mold is hot enough that the lead doesn't freeze to the mold surface, then cool to the middle, the shrinking while cooling will pull the boolit or parts thereof away from the mold instead of drawing metal from the sprue puddle. Undersized and/or deformed.

[geargnasher]

Looks like a cold cavity. Try alternating pours, fill the front first one time and the back first the next.......I have several iron molds that insist on alternation. Sometimes it's a vent issue or the sprue plate has more gap over one cavity than the other allowing one to vent better out the top.

I've also observed Rick's "heat shrink effect" many times, mostly on Lee moulds, where the edges of driving bands get a crystalline and rounded appearance, probably the antimony "shocking" out of the alloy due to excessive mould temps in places. This usually happens when casting well into the frosty stage.

You're running the ragged edge of too hot for the tin content you have as it is, so that certainly isn't the problem.

Gear

[cbrick]

Some alloys do that. My wheelweights, and 50/50 refuse to give me sharp corners unless I'm right at the edge of frosting. No nice and shiny with that alloy.

Hhmmm . . . Maybe it's the tin, I automatically add 2% Sn to all WW alloy, avatar is a good example of a well filled out and shiny WW boolit.

Rick

[lwknight]

The boolits don't look like the molds were too hot and the only drawback with tin is that you get shrunken bands when molds are just entirelytoo hot.
I've gotten the easiest casting with 5% tin. It casts best at lower temperatures like
under 650 all the way down to 600 if the molds are up to temp.
I would cast doubt on tin being the problem.

I had some bad alloy before that just would not cast a good boolit. I never knew what or why. I just made weights out of it and got another batch that worked just great.

[cbrick]

The boolits don't look like the molds were too hot and the only drawback with tin is that you get shrunken bands when molds are just entirelytoo hot.

No, I wasn't saying the molds were too hot, I said they were getting there and had a hot spot inside the cavity, keep casting at the same pace and it will soon be too hot.


I've gotten the easiest casting with 5% tin. It casts best at lower temperatures like under 650 all the way down to 600 if the molds are up to temp.

Sure, the higher the Sn percentage the lower both the melt/liquidus temp is, right down to 63/37 solder at 361 degrees. Also the slower the age hardening and the faster the age softening. But you are right, 5% tin alloy sure does make a purdy boolit.

Rick

[GP100man]

I`ll add this on smaller molds like sc 357 molds this happens faster & the fix for the smaller molds is turn the temp down to 625f- 650f or let the mold cool a 5 count .

I never thought of the antimony cookin off or avoidin heat.