first mold

[rollmyown]

I've just bought my 91/30 and have located some new brass. I'm keen to get started with some homebrew. To that end I want to get some comformation that I'm on the right track.

Slug the bore

get mold 3 or 4 thou over.

fit GC / size to 1 or 2 thou over.

Load , shoot

This will be my first custom mold, so I want it to be a good experience!

How much can a boolit be sized? If I get another rifle 2 or 3 thou less can I size smaller to suit another gun and expect good results?

How important is it to take a chamber cast when ordering a mold????


Thanks in advance - Rob

[JIMinPHX]

With a boolit design that has conventional lube grooves, I've gone down as far as about .005", but I did it in two steps. If you get a micro-groove or tumble-lube design boolit, then taking off .003" is enough to seriously reduce your lube carrying capacity.

[HORNET]

The mold doesn't have to cast .003/.004 over the bore size. Some find the absolute best accuracy with those that cast at bore size. A little over bore size does add more flexibility as to alloy composition without going undersize. Undersize is usually a very bad thing...
Buckshot has written that he's sized 8 mm boolits down to use in some of the larger .30 cal bores (about .008 reduction, IIRC) with good results.
FWIW, I've never done a chamber cast. I have slugged the throat on several rifles to get measurements, usually to see what the maximum neck diameter is for a loaded round.

[JIMinPHX]

There are a few tricks that you can pull to size a boolit down more than the usual couple of thousandths. If you fill the lube groove with lube before you size, that helps to prevent deformation of the lube groove. Sizing in steps, .002" or .003" at a time helps too. The harder the alloy, the more difficult it is to perform major size changes. Harder alloys sometimes need to be sized in smaller increments.

Eventually, you do hit a point where you can't make it work. For instance, you can't turn a .38 into a .30, at least not very well.

[sheepdog]

Rollmyown welcome to the board. If you like I can send you some Lee 185 grains 303s to try out.

[David2011]

A commercial caster I know said he accidentally ran a .44 boolit through his automated, air powered Star sizer and turned it into a .40- but would do it deliberately. It's hard on the lube grooves.

David

[rollmyown]

Thanks for the offer of the Lee 185 grainers Sheepdog.

I'll send an email!

Great advice folks!

[Buckshot]

[QUOTE=HORNET;835010]
Buckshot has written that he's sized 8 mm boolits down to use in some of the larger .30 cal bores (about .008 reduction, IIRC) with good results.
[QUOTE]

..........Yup, a Lyman 323470, a 165gr RN Loverin dropping at .325". Lube -sized to .323" and then squirted it up through a Lee .314" die. A push through is actually 'THE' most accurate sizing means I know of. This was for a ill dimensioned 7.65 Argentine that had a .303" bore and a .314" groove. The only fat 30 I had was the Lyman 314299 and it was just a bit over .301" on the nose. If the nose on a bore rider doesn't ride, it's only there to cause grief :-) That much reduced 8mm Lyman did a great job in the Argentine.

.............Buckshot