Hey, does anybody out there know how to make a chamber-throat cast without all the fuss and expense of Cerrosafe? There must be an easier way!
Ok.. your in luck.
Take a well fireformed case NOT resized and fill it with ww alloy or harder to just below the shoulder/neck junction.
Your need a pure LEAD bullet with some length. This is what's being compressed to form your impression.
Insert lead bullet litely lubed on the outside into the case and chamber the rd.
You need a rod just under groove dia.. the hardward store sells steel rods pretty cheap. Something a few inches longer that the barrel with faced off/square ends.
Wrap one end with a couple wraps of electrical tape or similar to make a nice fit to the grooves. This prevents the rod from going to the side or galling.
Take a piece of tissue paper or Kleenex and put a wad of around 1/2" comressed into the muzzle end. This compresses and cushions the action and prevents the rod from seizng on the end of the lead bullet.
Insert the wrapped end into the muzzle down to the lead slug-- now tap that rod with measured stokes with the buttstock on the floor--not hard... just even swings with little wrist action. Just enough to fully compress that lead slug. It'll bounce the same when the slug is compressed fully.
Open the action with care as NOT to deform the now impressed slug of your throat. That dab of lube will help.. I often leave the rod in the bore and as I open the action I litely poke the rod end on the wall to give it a boost. Easy does it as not to deform your impression.
The lead slug/bullet should neatly form to the dimensions of your throat and chamber origin and some of the rifling IF it's long enough. Reverse seating a bullet could give you can idea of how long a lead bullet to use IF the throat is very long. Most often their one caliber of length or less.