Did find reference to what you want to do on another forum. FL size 10mm,
then progressively bump it with a 357 sig die until it headspaces with the base
just below the barrel hood. Shoulder angle is not perfect---but it should go bang.
then progressively bump it with a 357 sig die until it headspaces with the base
just below the barrel hood. Shoulder angle is not perfect---but it should go bang.