.25-20 WCF mold woes

[jdsingleshot]

I'm having trouble getting my mold to cast without voids.

I have reconditioned a Winchester original .25-20 mold--Filed down the faces to reduce the oversize cavity, made a cherry and recut the cavity, cast a bullet and used it to lap the cavity.

When the mold fills, it makes nice smooth castings. At first I was only getting about 40% good results. After trying tactics such as holding the mold tight against the bottom-pour spigot, holding it loosely against it, leaving the mold in contact longer, etc. there was no noticeable improvement.

The last session, I filled the pot fuller to get more pressure and got about 60% good results.

I'm using WWs. I have .308 dia. and .314 dia. dies that cast perfect bullets from WWs.

My melting pot is at it's highest setting, but I'm not getting any frosted bullets.

What else can I try?

It just occurred to me, I had to make the sprue cutter. Would a larger hole in it help with mold filling?

[uscra112]

Does it need to be vented?

[jdsingleshot]

Logical question. Originally, it was not vented, but I scratched lines across both faces. Would the need for more venting allow some percentage of good pours and some bad ones?

[Bent Ramrod]

Try ladle casting. A lot of moulds don’t like bottom-pouring. I recently cast dozens of culls from a .44 Spl. single-cavity wadcutter out of a bottom-pour furnace. Adjusting the heat, varying the spout opening, pressure vs splashing all over, walking widdershins around the pot; all the secrets of master casters availed nothing. Finally I stuck a Lyman ladle in there, let it heat up and started casting with it. Same pot, same metal, perfect castings. I had cast good boolits with the bottom pour out of other moulds in the past; and I suppose there is some fundamental, underlying reason for the failure in this case, but I wanted boolits, not a research project. Only problem thereafter was getting the filled ladle in and out of the melt past the spout machinery.

Smoke the cavity with a BIC lighter or a candle. The thin layer of carbon keeps the heat from transferring as quickly, allowing the molten metal to completely fill the cavity before solidifying.

Keep casting. If you’ve freshed or lapped the cavity, it needs a layer of oxidation to build up again (also known as “seasoning”), which slows the heat transfer in the same way as the soot layer does. Properly seasoned, it likely will no longer need the smoking treatment. Also, some moulds simply need to be used for a while before they settle in.

Don’t drill out the sprue plate except as a last resort. You can pull the entire base of a small casting off-center by knocking the sprue off if the hole is too large.

[HWooldridge]

Are the voids consistent in their placement and appearance?

A consistent void points to a possible venting or filling issue. Voids on the bullet base at the sprue indicate insufficient metal left to feed the base, or the sprue puddle is freezing too quickly. Wrinkles usually point to a mold that isn't hot enough to allow filling prior to freezing. Random voids all over the place can stem from a contaminated melt (trash or incorrect metals present).

Any oil residue present on the mold faces can also cause filling problems. I had that happen a couple weeks ago on a 30 caliber iron mold - a quick shot of brake cleaner solved it.

[jdsingleshot]

Thanks to both for the suggestions and insight. I have a ladle and will try that next.

Voids are random and less than half the time, but annoying, of course.

[Good Cheer]

If you have it try adding some tin (small boolits, big blocks).

[jdsingleshot]

Today I tried the above suggestion to try ladle casting. SUCCESS! I got 80 good castings with only one early reject.

Don't understand why it worked, but don't really care either. I'm very pleased.

[jdsingleshot]

Thinking the bottom pour furnace may have been dumping lead so fast the venting could not keep up. Maybe the ladle, having a much smaller "head" of lead, pours slow enough for the mold to vent adequately. I'm happy. The mold was a fleabay buy and was missing the sprue cutter and its screw. The cavity was also out of round. I restored the mold hoping to get it usable.

I think I paid $35 for it, so I call it a bargain, since I enjoyed the challenge of putting in service.

[Larry Gibson]

With the recutting you probably used cutting oil (?). If so you need to better clean the mould. Clean with carburetor cleaner. When that has evaporated the run the flame of a propane torch over the mould blocks. You will see "moisture" come to the surface and evaporate. Once evaporated move to other areas until all the moisture has evaporated. Not need to overdo it as when the moisture evaporates that's it. When the blocks cool swab the cavities out with a clean Q-Tip to remove any deposits. Heat the mould to casting temp and cast. Keep the sprue plate hole about 1/2" from the furnace spout and let the stream of alloy get into the cavity as quick as possible. Alloy should be about 710 - 125 degrees. Let the alloy roil back up out of the cavity making a good large sprue, even if some alloy runs off the side.

[Bent Ramrod]

And don’t be broken-hearted if that doesn’t work, either.

I took advantage of my “automatic ink delivery” subscription to print out all the articles of interest in the CD collection of The Fouling Shot, the Journal for serious cast boolit shooters. Some of these articles cover the joys and sorrows of bottom-pour vs ladle boolit casting.

One poor guy, David Finch (No. 63, Pg 14), made a science project out of his casting woes. He spent a day with his favorite rifle mould, bottom-pour furnace and powder scale, casting (after proper preheating and other prep) 20 boolits each with the spout held against the mould, 1/8” from the mould, 1/4” from the mould, low flow, medium flow, high flow, etc, etc, etc. He inspected and weighed the castings, winding up with a lot of interesting data on surface finish, fillout, average and extreme weight spreads, and, as he put it, “Not a single bullet fit to put through my Hart barrel.”

He said he never had a problem with pistol boolits, but his Hoch .30 caliber was not going to cooperate. He remelted all the boolits, put his trusty Ideal ladle in the top of the furnace and cast 131 boolits, with only four rejects; the rest being within +-0.2 gr of the average weight. His Editor added a note that he hadn’t ladle cast in a while, so just for laughs, he fired up his furnace and ladle cast 81 boolits. He reported one reject.

Obviously, this issue has been going on for a while. You may find a sweet spot for your particular mould, alloy and temperature. Then again...

[jdsingleshot]

Evidently, “Deficient observation" is running loose this morning ;-). My last two posts noted that the mold is working perfectly with my ladle.

And, no, I did not use cutting oil when I recut the mold. There were only a couple of thousandths to remove, so no lubricant needed.

Problem is solved, so let's don't solve it some more.

[Green Frog]

If you have it try adding some tin (small boolits, big blocks).

^^^This was going to be my first suggestion.^^^ Second, if you still want to use that bottom pour pot, try holding the mouldaway from the spout by about a half inch or so. Don’t ask why, but this works for me.
Froggie

[Larry Gibson]

Evidently, “Deficient observation" is running loose this morning ;-). My last two posts noted that the mold is working perfectly with my ladle.

And, no, I did not use cutting oil when I recut the mold. There were only a couple of thousandths to remove, so no lubricant needed.

Problem is solved, so let's don't solve it some more.

The observation wasn't deficient. The response was in direct answer to to your first posts question;

"When the mold fills, it makes nice smooth castings. At first I was only getting about 40% good results. After trying tactics such as holding the mold tight against the bottom-pour spigot, holding it loosely against it, leaving the mold in contact longer, etc. there was no noticeable improvement.

The last session, I filled the pot fuller to get more pressure and got about 60% good results.

I'm using WWs. I have .308 dia. and .314 dia. dies that cast perfect bullets from WWs.

My melting pot is at it's highest setting, but I'm not getting any frosted bullets.

What else can I try?"

Make an observation there is no mention of ladle pouring in that post. You only mentioned your problems with the bottom pour and asked what else to try. My observation, actually a suggestion, was such. It was not a "deficient observation".

I'll make another suggestion if you want to use the bottom pour. If not, then please ignore and carry on with the ladle as you wish. You still might play a propane torch flame across the face of the mould blocks just to see if any "moisture" is there. You asked for help and I offered help, that's all.