Optimum cavity spacing?

[badgeredd]

I am having fits with a mold, which IMO has too little space between the cavities. Do you guys have an opinion on what is the optimum spacing, or better yet a best web thickness between cavities, say 30 caliber and larger?

I am well aware that with small bullets like a .22 one needs less space between cavities, as proven by a BRP mold I have. This mold is a larger cavity and the web between the cavities is barely 1/8". IMHO, the cavities are just too close together. What seems to be MY problem is that I can't seem to get a good bullet out of all of the cavities. Usually I have at least one bad casting per pour. What do you guys think?

Edd

[338RemUltraMag]

Edd,

My thoughts are anything 30 cal and smaller can have .100-.110 up to about 42 cal .125-.150 and over 44 cal at least .200 or more.

Josh

[Springfield]

What exactly is wrong with the castings? Except for overheating the molds I don't see any problem with them being too close.

[helice]

Hey Edd,
How many cavities? How big is the block? What is the block made of? Aluminum, brass, steel?

[BABore]

I ran into similar problems with my 4C molds and 0.460 boolits weighing more than 375 grains or so. I recommended going with a 3C mold made from 4C blocks. I have several that way and they pour great. The issue with big cavities too close together is the heat generated from the prior cavity's pour will create a hot side for the next cavity. It usually results in excessive frost on one side and suck back. When pouring a big 4C mold, I would pour every other cavity, wait a bit, then pour the other two. Running a cooler pot and more fan time between dump and repour helps too.

[btroj]

My general experience mirrors what BAbore said.

Excess heat thru a thin web makes for some bad bullets. Slower tempo, lots of fan time, and sometimes skipping cavities helps. My Lee 6 cav GB for a 420 gr 45-70 bullet gets real hot, real fast. I just slow way down to keep it from over heating.

[Dale53]

I have multi-cavity moulds for all of my handguns and many rifles. I have NEVER had a problem with them. I use Lee moulds, NEI, LBT, Mihec (my favorites) and NOE (excellent, too).

I DO use a manicurists fan placed so that it blows on my mould while I am emptying bullets. The mould maintains a constant casting temperature and I can run continuously without more than 2-3 second delay for the sprue to set.

I pre-heat my moulds and use the fan on all of them. Try it, you'll like it...

Dale53