Mold fill bullet texture and sprue

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  • Last Post 19 January 2009
Dave King posted this 03 January 2009

A few items up from:

I use straight wheel weights.

I have a Lyman bottom-pour furnace.

The mold is a Lyman 452424FV double-cavity.

I fill the mould by placing the sprue hole tight against the pour nipple then pull away at the first sign of complete fill (a little spurt) and add a little melt to make a decent sprue lump.

I use a wooden stick to knock the sprue cutter just after the melt frosts on the sprue plate.

I dump the bullets as soon as I cut the spue.

I vary the refill time (pacing - tempo) by a count to allow the mold to cool while it is empty.  I have a small (tiny) fan for cooling the mold.

I use a small loupe to visually inspect the bullets and return the culls to the melt once I've cast a fair pile (hundred or so). I have a fair cull rate, about 50% and sometimes more from this mold.

I use a commercial flux, Frankford Arsenal and flux at each add of new metal (culls or ingot).

Here are a few images of some bullets I just made and their weight distribution.

Seven bullets from the Lyman 452424FV double-cavity mold.  The weight of these seven, in grains, is 253.4 (x2), 253.8 (x2), 254.2 (x2) and 254.4.

Sorry about the poor quality images, I don't have a macro setup here at home.

 

 

Now some questions.

On the sprue I notice the cut looks grainy, not a clean shiny cut.  I suspect this is due to breaking the sprue off vice shearing it off but I'm not sure.  What do you believe to be the cause and effect of this type sprue (as seen in the 2 magnified images)?

In order to get the bullets (mold)  to fill completely I feel the melt might be pretty hot (I've ordered a thermometer).  I can clearly see the milling marks transferred from the mold to the final bullets.  The bullets also seem to be filled and have sharp definition at the edges.  Is this a “bad” thing, high temp and high mold definition?  Is this also perhaps due to my straight wheel weight alloy?

The texture of the bullets gives them a 'dull' appearance as compared to the shiny ones that have rounded edges and low mold definition.  If I go a little too long and allow the mold to get hot I get frosted bullets.  These frosted bullets seem to have a little less definition than the ones I retain as 'good' and have a whiteish type appearance.  Are the bullets I'm calling good, the examples above, frosted?

Any help with getting me going would be appreciated.

 

The distribution seems good to me with the weight being near the 255 of the mold design.

 

 Edit for spelling and clarity

 

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billwnr posted this 03 January 2009

Dave, I am real selective about my rifle bullets but don't believe there's any value in weighing handgun bullets. Just my opinion.

Your sprues might need to cool a bit more before you cut them.

Your bullets look good.

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Dave King posted this 03 January 2009

Thanks

I mostly weigh them to find voids, but with trying a new method I thought I'd see how I was doing with consistency. I still just dump them all into one pile of 'shooters' once they're weighed.

Voids give me fliers of course and I was getting them too often in my bullets I made for my .44. Since I've started weighing my bullets and culling the light ones I'm a lot happier.

In my previous method my bullets were averaging about 3 to 4 grains lighter than they are now. They were shiny but had rounded edges where they didn't fill out well. I believe the new method is better but I'm still too new at this to know much.

Thanks for the info on the sprue, I'll try letting them cool longer.

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RicinYakima posted this 03 January 2009

Dave,

I agree with Bill in that the sprue is just semi-solid when cut, so wait a second or more longer.

Frosty isn't bad, it just means that your bullet is cooling slower in a hot mould. Lightly frosted will help equalize weight, but your distribution is normal for a commercial two cavity mould.

Voids can be caused by small amounts of air trapped in the cavity. That is one of the problems with the technique you are using. If you would lessen the flow rate and leave 1/4 inch between outlet and top of the mould, you will have less chance of air trapped.

I use a small bread loaf tin to catch the overflow under the mould. I have the flow rate of my RCBS pot so that it take 1 to 1 1/2 seconds to fill a 255 grain cavity. When both cavities are filled, I let the lead flow over the top of the plate till I have a good sized puddle over both holes.

 HTH,  Ric

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Dave King posted this 03 January 2009

RY

Thanks

I haven't been able to get the mold to fill to my satisfaction without touching the mold to the nipple. I attribute the better fill to the extra weight (pressure) from the column of lead in the sealed delivery. If I leave a gap and pour-fill my bullets aren't well defined but perhaps this is due to the straight wheel weight alloy? Maybe if I add some (?) tin the mold will fill better in the pour-fill method. What do you think?

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JetMech posted this 03 January 2009

Dave,

I get a better fill-out if I add 2% tin to straight WW.

Bases are a little torn. As Bill and Ric said, wait a little longer to cut the sprue. I also get better results by cutting the sprue without hitting the sprue plate. Just open it with a gloved hand. Just cast 250 rifle bullets and the bases came out smooth. Once the mold was up to temp. the cull rate during visual inspection was 8%.

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Dave King posted this 03 January 2009

DB

Thanks

I'll see about adding some tin to my alloy.

The gloved hand sprue cutting sounds a little rough. I have to give a pretty good 'whack' with the wood mallet to cut the sprue and the lever on the Lyman mold is short so no real leverage as I see it. I'll still get a glove and give it a go though to try it out, maybe I'll build a new sprue plate with a long lever.

I visually inspect with a loupe and I'm pretty fussy but once I have a better understanding of the alloys and process maybe my acceptance percentage will go up with this mold.

For my .44's I have a Lyman 429215 single cavity gas check mold that turns out ~215 grain bullets with a low cull rate using the straight wheel weight alloy, I wish the others did as well as this one.

I've got a few items on order to help determine the variables, a thermometer and a hardness tester. I'll check with a local casting friend about availability of tin, I believe he uses plumber's solder.

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RicinYakima posted this 03 January 2009

Dave,

Like Dan said, 2% will make a major difference in fill out compared to WW's fluxed with commercial stuff. I have been using the 95% tin and 5% antimony solder from Grainger with complete satisfaction. Weigh it out on the postal scales. I also cast with a loose plate so that there is some air escape under it as that helps full bases as does having the sprue plate hotter than the mould, the reason I have large sprue puddles.

And adding to Dave's suggestion, I use my old Firefighters glove on my right hand. Once the mould is up to temperature, I lay may palm on top and push with the heel of my thumb. That makes even poor plates cut smooth and clean. It takes about ten pours to get hot enough not to have to hit it with a hammer handle.

HTH, Ric

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Wally Enga posted this 04 January 2009

Dave King wrote: The gloved hand sprue cutting sounds a little rough. I have to give a pretty good 'whack' with the wood mallet to cut the sprue and the lever on the Lyman mold is short so no real leverage as I see it. I'll still get a glove and give it a go though to try it out, maybe I'll build a new sprue plate with a long lever.  Dave

If your mold & sprue plate are up to casting temperature, it should be easy to snap open the plate on a double cavity with a gloved hand with only about 5 lbs or so of force ---- IF you do it as SOON as the sprue solidifies.

I don't know of anything “good” that happens if you wait from that point --- it's a solid already so it's not going down the hole and the longer you wait the more force to cut and higher chance you tear a “divot” out of the base especially in a hard alloy like linotype.

I place my molds on a cheap $10 electric hot plate, set to bring the mold up to a temp just hotter then my casting temp and the first fill's cut easily.

 If you have any problem with lead smears on the plate or mold top with this method, you will need a very thin layer of a high temp lube like “Bull Plate or similar.

 It's a good idea to use a high temp lube just to minimize wear on a mold anyway --- and about mandatory on an aluminum mold.   Try doing a few this way & let us know how it works out.

 Wally

 

 

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Dave King posted this 04 January 2009

Again thanks.

I'm headed to Home Depot today to round up some Plumber's solder and I'm going to dig around for leather gloves and a little hot plate while I'm in there. (Of course I'll need to get something for the house as my wife will be along too. A bauble, maybe some weather stripping or other easily visible home improvement item.)

I polish the surfaces of the factory sprue plates and use a little high temperature grease on the hinge area. They're adjusted to the point where they drop open by gravity when hot.

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JetMech posted this 04 January 2009

Just to follow up on what has already been said. I was hitting the sprue plate on my Lyman molds for 20 years. Had to wait a 15 seconds after pouring to get a good cut-off of the sprue, at the temps I was casting at.  I just started using the glove method and it works great. Like Wally said, as soon as the sprue is solid, cut it. You'll be casting a little faster then you've been used to. Increased casting rate is the icing on the cake as far as I'm concerned. Those beautifull bases are the main benefit.

I think the shock of hitting the sprue plate is what causes the bases to tear instead of cut smoothly.

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Lillard posted this 04 January 2009

Dollar Bill wrote: I think the shock of hitting the sprue plate is what causes the bases to tear instead of cut smoothly. I think you are right Bill, I use a welding glove insted of a whacker my bases are much smoother.

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CB posted this 04 January 2009

Dave King wrote: Again thanks.

I'm headed to Home Depot today to round up some Plumber's solder and I'm going to dig around for leather gloves and a little hot plate while I'm in there. I buy the nice Deer or Elk hide gloves for about $14 a pair. They are soft and remain fairly pliable after being exposed to heat. The softness lets me feel what I'm handling, being able to pick up a dime if I had to. They are restful to use through a 2 or 3 hour casting session.

I can momentarily touch anything hot while casting, even drop a bead of molten lead across a finger without ever being burnt. If the sprue becomes too hot to push open, I use a cotton shop rag folded in quarters, handy and not too big to hang up on stuff.......Dan

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Dave King posted this 04 January 2009

Great, thanks to all for the help.

Just back from Home Depot; got some double palm suede leather gloves, and trinkets (grass seed and a diesel fuel can).  I forgot about the hot plate in my haste to get away from the people.

I couldn't find any 95/5 (Tin/Antimony) solder, they had some 97/3 (Tin/Silver) so I left it there.

Good news for me is that I had 8 oz. of 95/5 (Sn/Sb) in my old tool box so I'll give a 2% Tin mix a try and break in my new gloves too.

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runfiverun posted this 04 January 2009

that 97/3 will work fine you are after the tin antimony and silver both add to the mix also but the amount in a full roll isn't even noticeable. you will only need the whole pound of solder to a 100 lb batch of ww's, if you get your mold and lead up to temp. about 750 is a nice temp for grey boolits in an iron mold after you get going then turn your temp down to about 700.

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gunarea posted this 04 January 2009

Hey Dave

   It's good to know I'm not alone in my compulsive endeavor to produce high quality cast projectiles. Although I have bowed to documentation proving handgun bullets need not be so perfect, it still gives great satisfaction to load those shiny perfect slugs. Both of the 44 bullets you mention are what I regularly cast along with a 320 gr. also in a lyman mould.

    Something that has worked for me over the last forty or so years, is letting the molten stream hit the side of the funnel and swirl into the mould like a toilet flushing. The air gap I am accustomed to is about an inch. The swirl will have an air vent in the vortex and when you master this technique, fill out becomes much less of a concern. It does take some practice to become good and consistent, but it is worth the effort to produce what you are wanting. I hope this will be of some help for you.

                                                                      Roy

  

Shoot often, Shoot well

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Dave King posted this 05 January 2009

Thanks

I tried the glove and twist open method, it works surprisingly well and it much nicer, certainly more quiet. The bullet bases are better, shiny and cut rather than grainy. I did need to wait a little longer and let the bullet cool to get the sprue to cut rather than pull away.

To have some idea how much tin to add I emplied the pot into ingots and weighed the ingots, 19lbs. As long as the pot was empty I cleaned it up well by scraping and brushing. I refilled the pot with 20lbs and added 2,800grains (.4lbs) of 95/5 solder.

On testing with the added tin and using the 1/4” air gap I initially felt really good about the bullets, they were shiny and appeared filled but upon inspection with the loupe they still had incomplete fill and weighed about 3 to 4 grains less than the straight wheel weight and high temp examples. I threw tham all back into the pot and tried again using the mold-to-nipple technique. The mold-to-nipple technique produced bullets that were also not completely filled in many cases.

I believe I may have moved the thermostat on the pot a bit during my cleaning and as a result now have a lower temperature. My thermometer will be here today and I'll get a good temperature reading so I can get some reproducibility in that realm.

I'm beginning to think I'm too fussy about the bullets but I have no high resolution images of others bullets for comparison. Could I impose and have someone, or several folks, post or email some hi-res images of pistol bullets for comparison.

Thanks

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JetMech posted this 05 January 2009

The increased tin and reduced casting temp will yield lighter bullets. Not to worry. I typically cast at 750-800 degrees so mine turn out a little frosted. After you get 100 or so bullets, weigh them and lay them out by weight and you should get something that resembles a bell curve.

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CB posted this 05 January 2009

Make sure your vent lines are clear. I run a razor blade down the vents, very lightly so I don't remove metal, but scrape out any hard build up.

Some molds I tap as I pour to help settle the lead into the corners. Do set the mold down immediately so the sprue puddle is not disturbed as it sucks lead down into the cavity as it solidifies.................Dan

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Dave King posted this 09 January 2009

I'm still learning.

The thermometer arrived, a Lyman. The melt temperature is about 720 degrees F. but I've varied it up a bit in a few tests.

I tried a run at between 750 and 800 as suggested and got bullets not unlike any other temperature, the sprue lump was a little flat and quick to run off the edge of the mold.

The little Lee lead hardness tester is a clunky but simple tool, several tests on my bullets seem to indicate they're about 11.8 Brinnel Hardness (wheel weights).

I'm back to my original fill technique of holding the mold tight against the bottom nipple for a short count until the mold is full them pulling away and making a sprue lump. This gives me full consistent weight bullets but with a fair number of culls. I'm still trying other methods but when I want bullets I revert to this method at present.

I'll try to get some macro pictures of the bullets produced by my attempts.

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CB posted this 09 January 2009

David,

You have gotten a lot of good advice from several people who know what they are talking about. Glad to see the forum working so well to help out.

I can't add much new to improve your cast technique but can't help but ask if you are aware that you are throwing away a heck of a lot of good bullets by your minute inspection and weighing. If casting museum quality bullets is your thing go for it. Whatever is fun is fun.

But if you are doing all that sorting thinking it will improve your pistol's accuracy you are probably wasting your time. If you want to find out, shoot several groups from a rest alternating groups of your near perfect bullets vs. groups of your culls and see if it's worth while.

Good shooting.

John

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