Lee mold casting WAY oversize

[Gunslinger]

I cast some boolits the other day (notice how many threads start with this sentence ;-)) from a Lee 6-banger 120 gr RN. The alloy was 3-1 WW-Lino. Here's the thing... some of the boolits are not round like they're supposed to be many of them are oval. I measured a bunch of them and got everything between .358 and .366. The oval ones measure .358 on one side and .363 on the other?!

I ran the pot pretty hot, and only used this one mold... and I think I used the speed casting technique. I did'nt get frostet boolits though... but I'm thinking that maybe everything was just too hot! Can hot temperatures result in the mold expanding up to .009"??

Needless to say they were almost impossible to size... and they looked very strange when sized!

[243winxb]

If the alloy is very hot , with frosted bullets, bullet diameter would be smaller then if using a cooler alloy. Putting pure lead in the alloy will cause more shrinkage on cooling, smaller diameter bullets. As far as being oval, depents on what side is large. Are these 9mm or 357 bullets? From Lee Website>
Mold diameter tolerance

Our bullet mold tolerance is stated diameter, +.003/-.000 inch. We gauge our bullet molds with a "go/nogo" gauge, which tends to result in bullet molds that run on the high side of the tolerance. You could probably use one of our standard molds at as-cast diameter with good results.

If the bullets are oversize or out of round the mold is not fully closing. A build up of lube, splash of lead, or a burr on the mold block faces are holding them apart. Inspect the mold block faces and carefully remove anything that might hold the mold apart. Make sure to lubricate the locating pins with solid alox/beeswax bullet lube, Lee part number 90007. If these steps are followed the bullets will cast dimensionally correct.

[Leftoverdj]

Most likely your mould is not being fully closed. This can be caused by debris or by the locator pins being too far out.

[Gunslinger]

Locator pins.... hmmm... Is it the small ones on each side of the mold block that goes in the holes on the opposite block??

[Shiloh]

Locator pins.... hmmm... Is it the small ones on each side of the mold block that goes in the holes on the opposite block??

Yes. When you lube the sprue plate and pivots, don't forget these.

As already stated, see if there is a small piece of lead, compressed almost foil thin, that is stuck on the mold. it just take a small piece to keep it from closing. Carefully remove it, a razor blade works, without gouging the mold.

Shiloh

[odoh]

Had a similar experience just yesterday w/a new RCBS iron block mould. Even before the first pour I knew there would be finning as I could see daylight thru the nose area. Of course I read the packup data afterwards ~ suggested that as part of the cast routine to tap the side of the mould handle to drive the block halves closed ~ as part of a break-in process ~ will see

[runfiverun]

the new [2] rcbs molds i have gotten lately have had the pins stick out, and i have had to knock them back some.

[Bret4207]

I ran the pot pretty hot, and only used this one mold... and I think I used the speed casting technique. I did'nt get frostet boolits though... but I'm thinking that maybe everything was just too hot! Can hot temperatures result in the mold expanding up to .009"??


The other guys covered what the most likely cause of the odd boolits is. As for the 'heat" issue- if you were running the pot hot and had a good hot alloy, and doing the Bruce B Speedcasting method, and weren't getting frosted boolits then the mould was running cool. You weren't getting it warm enough. The faster you cast and dump, cast and dump, cast and dump the more the temp will rise in your mould. Now that is assuming you had a good rhythm going and weren't sitting there with the mould open looking at your boolits. The more the hot alloy stays in you mould the more it warms. There should come a point where the boolits start frosting. At that point you can either slow a bit or hold the mould on the cloth a bit longer to cool it or turn the pot down a little. Personally I just slow down a little or more likely, just keep casting as frosty boolit don't bother me at all in most moulds. If you were holding the mould on the wet cloth too long that could keep it from coming to heat also. All you do is just touch the sprue to the cloth for a second, it's not like you were branding a cow in a western.

Try to get your mould a bit hotter and see if they don't fill better and look better overall.

[rhead]

One other thing that can cause this with a Lee six banger is pressure on the sprue plate handle. If it is depressed even lightly while filling the cam opener will be activated a bit and cause oversized, out of round boolits.
Just one other thing to throw into the mix. At least it is easy to fix.