The old hammer dies are similar to bench rest dies like Wilson. If you hone them for your rifle they produce very accurate loads as everything is inline and supported during loading.
New brass use a conventional sizer first if it is oversize. Most of it is either SAAMIE spec or undersized so the collet will work fine. For some reason 300 Winchester brass always seems to be on the short side so needs fire forming.
To a ridiculous degree IMO.
