56-50 bullet mould

[morerams]

On reading the posts I have found regarding bullet moulds I haven't seen the RCBS mould mentioned, they seem to make a suitable one, 350 grain 512 dia, is there a reason for that?
Allan

[El Supremo]

Hello, Morerams;

First get input from HERBERT, down your way.  Try a PM. 
Part of the answer involves bore dimensions that can vary.

My limited experience favors a bullet with more lube capacity than the RCBS.
If select RCBS watch that the sprue plate HOLE aligns with the center of the cavity, not way off to one side.

Look at Accurate Bullet Molds' 51-320S and 51-350S to see what lube capacity means.
The 320S is a little shorter to allow more powder for a given ctg OAL.
Accurate CNC bores for dimensional consistency.  They permit small changes, too.  Nice.
Only deal via email off their site.  I like their work!

The Lyman 515 types for 50-70 can be lacking on lube capacity, cast large and need excessive sizing. 

Rapine made a 350-T,  that is out of production, was liked for lube capacity.  Might find one used.

Dave Gullo at BUFFALO is very knowledgeable and worth contacting for suggestions.

Get to Herbert.

All the best,
El Supremo/Kevin Tinny

[Herbert]

The bullet mould needed will depend on what model Spencer you have and who made it,originals have a longer OAL cartridge than the Italian ones and it is also important to match twist rate to bullet length also slugging the bore is a good plan .512 is too small for most Spencers but not all

[morerams]

Thanks Herbert,
                       I have a Spencer built M1865 and have measured the barrel, it is very close to .512 groove diameter.
Allan

[El Supremo]

Hello, Morerams:

Nice to see Herbert.

With your GROOVE being .512", most would suggest a sized bullet OD of .001"  - .002" over that in 20 or 30 to 1 alloy.

My Spencer 56-50 experience favors 20 parts lead to 1 part tin, both truly PURE, that CASTS .001" larger than the desired SIZED OD of .513" - .514"

I like a final sized OD of .001" - .0015" over groove diameter, which means your 20:1, AS-cast before sizing OD should be .512" +.0015" + another .001" (for sizing cleanup) = .5145" (as cast od), - .001" sizing = .5135". Whew!

Now, to get THAT .5145" as-cast diameter that cleans-up .001" to .5135", the mould has to be LARGER than .5145" to account for linear shrinkage.  A .500" bullet in 20:1 alloy, can have linear shrink of another .0015" - .002", per metallurgical tables, but I find that if I specify "the mold should cast Lyman (new) #2 alloy to an as-cast od of .514" .5145", custom mould places like Accurate will know the shrink compensation and bore the cavity TO CAST TO your desired AS-CAST DIAMETER of .514" - .515".

You do not want your mold to "drop" castings that are too small. 

If you ask most mould makers what their blocks cast TO in Lyman (new) #2 alloy, you might hear mush.
But Accurate has been so close and with no shift in the parting line, that my bullets have been right-on. 
Then your bullet mould will cast bullets that can be sized to the proper diameter.

Herbert's near you.  Maybe he can supply some sample OD bullets to try or
he may know a readily available mould that will be ok.

All the best,
El Supremo/Kevin Tinny