.458 SOCOM and cast boolits

[dh2]

I have a project going to build a .458 SOCOM AR-15 upper receiver the barrel is being shipped at this time, So to day I started loading some test ammo I have a Lee die set and loaded 20 rounds in new starline brass with some 300gr. Rem. HP's I had for my 45-70 and noticed they case necks on these are very tight, which is fine for J-words. where the problem comes in is that I have a cast boolit mold for this round from Accurate I am casting with it but want the barrel here to slug it before I size them. But with the neck being so tight on the cases I think it would destroy a cast boolit before it went the case. My .458 Win. Mag. and 45-70 Lyman M die will not go down far enough for this short case. I am expecting to get a .460 neck expander for the Lee expander die from NOE some time when I put in an order. I am sure some one on here has run in to this before or has an idea how to deal with it, short of putting in an order for $7.00 from NOE and most likely get charged more for shipping than the part. thanks

[dkf]

Yes the neck on new brass is super tight. You can get by with the expander that comes with the Lee set for jacketed but it is kinda short. I use the NOE expander plugs for the universal flare die, I have several different sizes. They also fit in the Lee expander die that comes with the Lee die set. I even expand the necks on new cases for jacketed bullets with the .459/.455 before loading them.

[curator]

In my experience, Starline brass needs to have the case mouths annealed before they will seal powder gas shooting lead boolits. Also, as you mention, if loaded using dies/expander designed for jacketed, they will size your boolits down enough to cause leading.

[oger]

Picked up a SOCOM expander, powder drop from Dillon and use their powder measure on a T-7 press. The Dillon will lightly flare the case and allow the gas check to enter the case easily so far it works well with the expander removed from the Redding sizing die.