Mold and Alloy Temp for Lyman 4 cavity molds

[Colorado4wheel]

I have a metal probe temp gauge that is very accuarte. I am curious if anyone else has figured out what temp their Lyman 4 cavity molds like to be at while casting. I tend to get mine hot on a hotplate till about 275-300F. Then with the 750F lead I get good bullets pretty quick. I have to swirl the metal in to avoid hot spots on the mold. Mold tends to stabalize at 275F after some casting. If the lead gets below 700F or so they just don't fill out the same. This is using mostly range scrap metal. Any thoughts? Is this typical? Should I be looking at trying something else?

[jsizemore]

What alloy are you using?

Clip-on WW with 1 1/2% added pewter gives me complete fillout at 650deg F.

[Colorado4wheel]

Range Scrap. Softer then WW.

[casterofboolits]

I have approx eighty Lyman four cavity moulds from 09 to 45C.

Every one of them likes to run HOT! That said, I always cast using three of the four cavity moulds in series. IE two 38-150-SWC and a 38-158-RN or vice versa. The pot temp is close to 800 deg. This helps to maintain even temps for the moulds.

The 44's and 45's need a bit of cooling and I dump the boolits, set the open mold on a small squirrel cage blower attached to the casting bench and continue casting, by the time I empty and fill the other two moulds, the one on the blower is ready to go back into the rotation.

Note: A bit of tin added to your alloy will also help boolit fill out.

I love iron moulds and hate aluminum moulds. :bigsmyl2:

:cbpour:

[Colorado4wheel]

OK, Thanks

Here is my plan then. I have 2 molds to work with both making my 9mm 147gr bullets that I shoot a lot of. My plan was to get them up to temp, which for me is mold at around 300F and lead around 750F. I have never tried hotter. The 750F lead will then even the mold temp out pretty quickly (hotplate doesn't get the mold up to temp perfectly evenly). Then just start casting. While the one sprue is cooling I will be emptying the other and refilling it. Then set it on the steal heat sink and empty the other one. Over and over. I may try the lead at 800F but I worry about casting too hot.

[AZ-Stew]

Lots o' imprecise info being passed around here.

First, range scrap runs closer to pure lead than it does to WW, so a higher pot temp is indicated. Not astronomical, but certainly above 700 degrees. Now, that 700 degrees I mention is a measured liquid alloy temp, not the number on the dial of a Lee casting pot. I've had Lee 10 pounders, Lee 20 pounders and an RCBS 20 pounder. Without question, the RCBS dial markings are closer to the thermometer-measured temperature of the alloy than are the arbitrary markings on the Lee pots. In addition, the RCBS holds a smaller temperature range as the thermostat cycles. Go back and read the individual posts to this thread with those thoughts in mind.

Now, I'll tell you outright that I've had my RCBS set on the same dial marking (750, which measures pretty close with a thermocouple thermometer) for almost two years and have cast pure lead, WW and linotype with it, in moulds from .22 55gr fpgc through .44 round ball and .45 SWCs and RNs at 230 - 250 grains. All castings produced good boolits. It's a matter of casting technique and speed.

For those boolits that take up a large portion of the mould volume (.44s and .45s), a slower casting pace is required to prevent overheating of the mould. Overheating is indicated by frosting of the surface of the boolit. Overall, uniform, dull gray appearance is fine, but a crystalline surface indicates overheating. This is more of a problem if the frosting is confined to a few spots around the boolit. If you look carefully when lube/sizing, you'll see boolit lube span the driving bands when there is a frosted spot that also crosses the bands. This allows blow-by and throws the boolit off balance because there is a low spot in the boolit surface at the point of the frosting.

A faster casting pace is needed for boolits that account for a very small portion of the mould volume. My RCBS .22 mould is a fine example. I have to cast fast to keep enough heat in the mould to prevent wrinkling. There's somewhat of a "cheat factor" involved here, though, as I cast those from linotype, which is really hard to cast bad boolits from. Almost any temperature will do. I still have to run fast at first, culling the raisins later, to get the mould up to temp. Once I'm on track with the mould temp, I can cast for hours at a relatively leisurely pace.

Pure lead balls for my cap & ball revolvers require a hot mould, but their volume with relation to the mould is high, so they will also cast well once the mould is up to temp. Cast fast and cull the wrinklies later.

Maybe there should be more to this post, but I just got called for supper. I'll re-read it later and fill in what's missing.

Regards,

Stew

[Colorado4wheel]

I am not guessing at the temp. I am using a Lyman Temp Gauge. I am not getting frosted bullets at 750F so it's not as hot as some of the stuff I did with a Lee mold a while back. I know that range scrap is closer to pure lead but it's not as soft after water dropping as my WW with out water dropping. Kinda in the middle which is perfect for my use.

[GSM]

The 4 cavity Lymans I have seem to have a real preference for high temps - just as casterofboolits mentioned.

Alloy: 80 ww / 20 lino

Thermometer reading: 730+/-

Frustrating until you crack the code of what the mold wants - write it down after you figure it out, too. Each one is a little different.

[leadman]

I found my Lyman 4 cavity molds like temps about 750' and more tin than my other molds.
Especially the 429421.

[Bret4207]

I've never seen any mould that like to cast cool. IMO, same as Stews, you control boolit quality by casting speed and mould temp. Pot temp is relatively unimportant. I'm sure you can have a pot at 760-800 degrees or hotter and still get wrinkled boolits.

I've often thought about getting a measurement of my mould temps, but in reality it wouldn't mean much. I can see at a glance if my mould is too cool or hot. What more do we need?

[AZ-Stew]

I knew there was something else I wanted to add.

The only difference I see between Lyman 2 and 4 cavity moulds is that it takes longer to get the 4-bangers up to temp and they lose heat a bit faster than the 2-bangers. Again, this is due to the ratio of cavity volume to the overall volume of iron in the mould. The mould (any mould) is a big heat sink. The smaller the casting, the faster you have to cast to keep enough thermal energy in the mould to keep it up to casting temperature. Cast slowly with a mould that throws a small boolit and the heat is drawn away and dissipated to the surrounding air faster than it is replenished. The result is that the mould cools.

Regards,

Stew

[Colorado4wheel]

So I guess no one measures the mold temp as a way of know when the bllets should start looking right. Once underway I don't measure, but after any break I get the measurement until it hits 275F just so I know the mold is about at the right temp to make good bullets.