Defective Mold?

[max range]

I bought a Lee 2 cavity mold for my newly aquired S&W .41 mag. Since no one has jacketed boolits or even loaded ammo for that matter. I have been reloading for many years, and casting (off and on) for more than two decades. I have a dozen molds from H&G, Lyman, RCBS, Lee and custom ones.

I have a large amount of COWW, Linotype and pure lead. Not an expert, but its not my first rodeo and I am stumped.

I degreased and smoked the new Lee mold, fired up my pot, fluxed it and began pouring the brand new .41 mold and my tried and true Lee 6 cavity 45acp 200 grain mold. The new .41 mold would not fill the rear (closest to the handle) cavity. I tried getting it hot, I tried letting it cool no luck. Meanwhile the big mold threw perfect boolits quickly.

The problem with the .41 mold is it would stop allowing lead into the cavity at the last micro second. Leaving an 1/8" gap.

Meanwhile the big mold was cranking them out.

After I ran about 8 lbs of lead I shut down. When I fished the boolits out of the water trap the .41 boolits measured .407-.408. Now is where you say my alloy was responsible for the shrinkage. Wrong. The .452 boolits measured .455 on the button. We can rule out the alloy.

As mentioned, I let the offending mold cool, I ran it hot, it made no difference. The back mold wouldnt fill not matter what I did, and it subsequently threw both cavities, too small and they are unusable.

Do I have a defective mold? What could I have possibly done wrong?

[Ben]

Are you casting with a dipper or a bottom pour pot ?

[max range]

Dipper. I tried several. One which held enough for two cavities, and another which would pour 6.

[Ben]

Is the sprue plate on the top of the mold tight ?

Sounds like air is being trapped in the mold and can't escape.

Did you hold the dipper for 3 seconds or so to give the cavities plenty of time for fill ?

[max range]

I will check the plate though it functioned properly. I poured until it would take no more and an adequate sized puddle formed on the sprue plate.

[max range]

Even so, what could explain the .41 mold throwing boolits smaller than advertised, but another Lee mold produced boolits in the proper dimension?

[GLL]

Experiment:

Reclean the mold completely. Loosen the sprue plate very slightly. Do not smoke the cavities and try casting JUST the the back cavity with pure linotype. See if this allows that back cavity to vent and fill out. If this works then retry it with COWW with a small dash of linotype.

Jerry

[GoodOlBoy]

If all of that doesn't work contact lee and tell them you are not getting the correct size out of the mold, and you are having fill problem.

GoodOlBoy

[runfiverun]

it sounds like a venting issue to me.
the mold is not taking the alloy from what I read.
anyway I'd definitely look at how level the sprue plate is and see if there is something just not right with the mold.

I recently got a 2 cavity lee mold and could see a sliver of day-light through the cavity's and thought oh-oh but it seems to cast just fine without the finning I thought I'd see.

[Ben]

it sounds like a venting issue to me.
the mold is not taking the alloy from what I read.
anyway I'd definitely look at how level the sprue plate is and see if there is something just not right with the mold.

I recently got a 2 cavity lee mold and could see a sliver of day-light through the cavity's and thought oh-oh but it seems to cast just fine without the finning I thought I'd see.

it sounds like a venting issue to me.

About a 99.9 % chance that is the problem !

Ben

[TXGunNut]

Venting. Lead goes in, air must come out. Doesn't need much but it needs some clearance.

[1johnlb]

That would have to be one super tight spru plate. Air will go places that nothing else will. My .02 is oil still in the mold or a defective mold. Ive had one defective mold from lee, the 303 Brit, to big to accept a GC. One out of a 5gal bucket full. Just my .02.