Change boolit size by changing the casting alloy

[rockydoc]

Is it possible to change the dimension of a cast boolit by varying the alloy mix, casting temp., quenching technique, etc.

I am casting boolits from straight outdoor range scrap that tests <10 BHN by pencil test(Stedtler pencil set..3B digs in, 4B slides ==4B, <10).
Cast in Lee TL.430-240 2 hole mold @ 860*F. The boolits weigh 238-238.5 grains and measure .4305" the day after cast.

I have measured the cylinder throats of my S&W 629-4" with pin gages at a consistent .4288 for all cylinders. The barrel bore is .4105, not the lands which I didn't measure.
Is a .4305 boolit too large for a .42288 cylinder throat? It would seem that those throats would like a .429 boolit.

If I could change the dimension of a cast boolit by changing alloy and technique to cast a smaller boolit it would sure beat having to buy another mold. I could size them to .429, but I would like to load as cast if possible.

Is it possible to change the dimension of cast boolits by varying the alloy mix, the casting temp, quenching technique, etc. ?

Rockydoc

[Don Purcell]

Most definitely can change diameter with alloy and temperature. Find out what the groove diameter is on the barrel. You will need to slug the barrel with a pure lead bullet or muzzleloading ball. Even though S&W uses 5 grooves you can still measure it, find a machinist if you aren't able to. Whatever the groove diameter is make sure the cylinder throats are .001 to .002 larger. I have a Colt Single Action .44 Special that has a .428 barrel with .433 cylinder throats. I size cast bullets to .432 and it shoots fine. Having undersize throats in comparison to the barrel will not do you much good. Don't be surprised if you have to have the throats reamed a couple of thousandths larger. All the best, Don

[TomAM]

Diameter is easily changed a bit by adjusting the percentage of tin.
Range scrap usually has very little tin, so there is not much potential to make it cast smaller by adding lead.

There is absolutely no need for you to change it, though.
.0017" larger than chamber mouth diameter is not a problem at all.

[PBaholic]

Softer lead shrinks more when it cools. That's why Linotype was so much harder, to prevent shrinkage in the type. I buy harder lead, and mix it with my softer stuff to get what I'm looking for. 1 lb of BHN 10 and 1 lb of BHN 20 will give you 2 lbs of BHN 15. You can also find some tin and add it to your mix. Pewter is mostly tin, as are some non-lead solders. There is a guy selling tin ingots on the for sale section.

166716

[44man]

You need to know GROOVE, not bore. your bore can not be right for a .44 either. Most S&W's are .429" groove, subtract about .006" for grooves and you have .423". Deeper rifling still takes you to .421" bore.
Whatever, your throats are too small for even a .429" groove. Throats make the worst size dies ever.
I take it you stuck some pin gauges in the barrel.
If you got .4105" and had crazy .005" grooves, you still have .4205". Most grooves are .003" deep. Add .006" to bore and you would have .4165". Sure the marks on the gun don't say .41 mag?
Something does not make sense, you did something wrong.