Question for Boolit Casters

[SgtDog0311]

OK… got a few hours to cast with a new mold and I’m a little surprised. I’m by no means an expert but I’ve got ten molds and cast for each of the calibers in my Marlin levers and most of the time with all but this new one the edge of the bases fill out very tight in the mold and drop with a crisp edge. If I have a bit of role-over on the gas checked bullets I don’t always reject those but I normally do with the plain base.

This LBT mold for my 38-55 is a two cavity with one being gas checked and the other being plain base. The thing is I cast about 150 of each today and virtually all of them came out with some role-over. They are pretty uniform so I think they wouldn’t be out of balance but I’m just wondering. At first I thought it was the temp and went both up and down but no real change. I cast this session with straight ww.

Any thoughts after looking at the pictures would be appreciated. I’m curious if the casters out here think this is a problem or not?

[William Yanda]

Tell us about your alloy, and any temperature issues while casting. I am eager to learn from your experience.
Bill

[bhn22]

I suspect you don't have the mold hot enough, or perhaps you're lacking in tin. LBT molds are extremely well vented.

[Pb2au]

I'm thinking you might be a bit cool on the mold temp. +1 for also wondering what your alloy is.

[slim1836]

He did mention using straight WW, I suspect more tin needed and/or hotter mold. Perhaps speeding up casting would keep the mold hotter.

Slim

[wv109323]

What the others have said plus the sprue plate may be a little cold.

[SgtDog0311]

Thanks for the input fellahs. Yes... straight Wheel Weight. Went hotter and colder. Speeded up cadence and slowed down cadence. Sprue place was hot enough that my cadence was often controlled by how long I had to wait for the sprue puddle to firm up. And venting is NOT the problem on my other LBTs, so point taken. On the tin, maybe. Not sure why I’m having the problem with only this mold though. And I didn't have very many culls for other reasons after I weighed and inspected either. One suggestion I've heard is to try the mold closer to the bottom pour spout. I'd almost be in my puddle but I'll give that a try. I'm just not believing the balance is going to be a 'big' issue since the weight on both cavities was within 1.2 grain with only a palm full of rejects out of 250. But I'd still like to know why!

Gas Check weight curve
94772


Plain Base weight curve
94773

I don't think these pictures are relevant but I took the time to show myself the weight distribution was not any different than when the fill-out at the base is what I've come to expect.

[Bloodman14]

They sat that 'a picture is worth a thousand words'; those two speak volumes! On the plain based curve, take the two 'spikes' and use for hunting/intended purpose, and the rest for plinking. On the GC ones, ditto. I agree with the tin question, you don't have enough, get your mold hotter, too.

[youngda9]

Hotter mold, add tin.

[Wayne Smith]

Just for interest, I have a Lyman 459122 Gould HP that requires pressure pouring with a ladle. Anything else and I get rounded bases. Pressure pour and every one is perfect. I run either pure ww or 50/50 and the same is true for both.

[trixter]

So if you were to load and shoot all of those, what will the difference in accuracy in the different weight groups? Just curious. Is it something the "average Joe-shooter" will even be able to tell?

[1Shirt]

Hotter like they say! Nice pics SgtDog! Good bell curve of reality!
1Shirt!

[Foto Joe]

Although I haven't been at it as long as some here on the forum, my learning curve has been steep to say the least. A month or so ago I experimented and started adding 2% tin to my COWW and went from what Larry Gibson refers to as "Good Boolits" to "Great Boolits".

Add the tin and and I think you'll find that things will improve noticeably even at the same temperature that you're running now.

[mdi]

Just wonderin' about a new-to-me phrase "role-over"? Or "roll-over"? Can't say I'm sure about what you mean....

[Foto Joe]

I think what he means is that the boolit bases are rounded and not filling out to the edges of the top of the mold blocks, i.e. the based appeared "rolled over".

[TMenezes]

I haven't heard that "roll over" term before but he just means the bottom edge of the bullet is somewhat rounded instead of nice and sharp.

Sir Sgtdog I am thinking that for whatever reason you have a mold that just needs a bit more tin than your other molds. One thing to check though is the bullet diameter. I notice my rounded edge bullets usually have a slightly smaller diameter than the rounded ones. If this is the case then that could be an issue. If not then it shouldn't be a big deal and you will just have to decide if its worth the extra cost of added tin to have that perfectly formed edge.

A less likely but possible problem is if your bottom pour pot gets a bit of grit in the nozzle it can alter the flow of lead just enough from one pour to the next. This is causing some inconsistency in my bullets, especially with the base. I am planning to take mine apart and clean it but just haven't had the time.

[DLCTEX]

Heat that mould on a hot plate. I see no hint of frosting so you haven't reached hot with the mould yet. Also try leaving a big sprue puddle and then try pressure pouring by holding the mould against the spout.

[SgtDog0311]

Ok… thanks again fellahs for the input.

That’s four votes for more tin, Gunerd, youngda9, Foto Joe and TMenezes; and three votes for a “hotter mold”.

1Shirt – thanks for the complement on the photos. I usually don’t get them as clear.

Foto Joe, I try and pay attention to what Gibson says.

Wayne Smith: What is pressure pouring? I’m not familiar with that one and sounds interesting.

Trixter, Like you, I’m not sure if I will be able to discern the accuracy issue or not. I don’t much shoot off a sled and this one is a 115 yr old 1893 so won’t ever wear a scope, even for load development so maybe the delta in filled or “rolled-over” won’t be anything I could detect. But I do have some samples targets to compare (this being one) once I make it to the range.
94780

If I can’t replicate those, then I’ll be determined to correct it or live with it. At any rate I’ll try the suggestions given for sure.

mdi, Just trying to describe it best I can. Foto Joe does a better job than me.

TMenezes, I kinda hope your experience applies - and if I fix it I DO increase the diameters a bit. That one is a whole other topic for this mold, that being that I’m a little disappointed in the diameter. This mold was made from an excellent chamber cast that I sent into Veral.
94779

The slug portion diameter of the chamber cast is .3785 and the size mold he chose to make from that was this mold, which drops at .379+ (+ being not quite a half). I was expecting .380 or bigger. So if I solved the riddle here with more tin or whatever, then bigger would be better in my opinion. I’m suspecting that he settled on the size to accommodate an abrupt throat and who knows, maybe it will shoot fine but I thought, for the plain base in particular, that I’d want a larger size. I’d rather have modified the throat than not have a tight fit. Veral obviously knows more than me so I’ll shoot these before I go lapping the mold or anything else. And if the tin did result in larger diameter that caused issues at the throat then I can just lap the throat, which again is a whole other topic.

Thanks again fellahs!

[SgtDog0311]

DLCTEX, You are right... I kept thinking I'd see some frost as I turned the temp up but quit going up as the sprue puddle took longer and longer to cool. I did use a hot plate (toaster oven actually) but I can go hotter. I was keeping a large puddle too.

Now I know what pressure pouring is. Thanks! I'll give it a try.

[oso]

I've seen this before and it may not be a problem but if it bothers you then at least degrease the bottom of the sprue plate and the top of the mold, if no improvement lightly smoke the bottom of the sprue plate with a butane lighter and see what happens (easy enough to wipe off the soot later), and if no change try running the tip of a soft graphite pencil around the edge of the cavity. This sequential approach may help isolate the reason this is happening with this mold. If you use sprue plate lube, use it very sparingly before dumping the boolits and wipe it off.

[SgtDog0311]

Thanks oso, all easy adjustments. Appreciate the input.

[Frozone]

If it's on one side consistently, and not the whole base, I bet you hold the mold at a small angle.
Try loosening the sprue plate a little for better venting of the last little bit.

[Changeling]

I've always found Veral to be a very fair man. If you have a problem I strongly suggest you email him concerning it!

[Echo]

I call 'em 'roundheels'. Agree with not hot enough and/or too much surface tension (not enough Sn). The way I tell if the sprue plate is too hot is when the sprue alloy flows off the plate like water! Time to cool it down (lay upside down on a wet rag and let it steam for a few seconds). Too cold is when roundheels start showing up (among other things).

[guicksylver]

I'll go along with Wayne S. (Kinda) If you have to pressure pour then something is not hot enough OR your pour rate could be too slow.

With large boolits like these you need volume to maintain a hot stream, by the time the alloy makes it to the top of the mold the stream and boolit body have already started to cool off.

Just for grins back off the sprue plate screw and see what happens.

All the advice you have gotten is good.

Try to remember EVERY mold has its own personality.

Good luck

[a.squibload]

I have a 2 cavity mold that likes pressure-pour in one & swirl in the other.

Try some cheap pewter from the thrift store, even less than 1% seems to help.

[SgtDog0311]

Frozone, actually the "roundheels" are quite uniform, at least from a visual inspection. And I think (don't know, just think) the weight distribution of the entire session would show it more if they were not.

Changeling, I've found Veral to be the same. Thanks! Want to be sure it's not the bonehead on the end of the handles first. Perplexing to me was in having a couple LBTs for the 45 Colt, and one each for the 32-20 and 32-40 and never experiencing this…

I'm suspecting venting, even with the generous venting Veral cuts in the top. Could be my fault – if I neglected to clean the underside of the Sprue plate well enough. As for heat there… I'm pouring a Sprue puddle as large as it will go without overflow and I'm keeping the sprue hot enough to make for a very slow cool-down. For Echo.. I've HAVE had it hot enough to run like water... no impact to the heels, much as it surprised me.

So, I’ll loosen it – try it. Clean it – try it. Smoke it – try it. Lightly touch the corners of the mold top with a file – try it. All those are reasonable first-step suggestions picked up from you gents either in this thread or on MO. I'll do all that running the batch a little hotter and starting with hotter mold. If that does not do it then next step will be the tin.

For you fellahs suggesting I add tin, don’t think I’m stubborn on that. Just don't want to incur more costs or have a different mix for this one mold if that’s not my issue. Not till I'm sure anyway. Just don’t want anyone to think I don’t appreciate that suggestion or that I’m too stubborn to follow up on it. I will if I can’t adjust it out of the mold with technique or otherwise.

Too cold here for this fellah to work in the garage just now but I'll post what I find when I do. Again, Appreciate all your input. It's been very helpful.

[Greg B.]

I don't hesitate to pour with overflow and find I get better fill. Sometimes when the sprew plate screw gets loose on some of my moulds I get a bit of flashing on the boolit bases which is just the opposite of the bevel you are describing. Veral also has a question and answer section on the "Greybeards Outdoor" site and this would be an interesting question to ask him.