Chamber cast or impact slug?

[aap2]

I was wondering if making an impact slug of a rifles throat is a better/worse method of measuring throat diameter etc., as opposed to just making a Cerrosafe chamber casting? I know that I have to wait 1 hour before measuring the casting and that after 1 month it expands quite a bit..any opinions as to which method is best?

[Outpost75]

If you are going to send the upset slug to the mold maker to ensure proper fit, LBT and others seem to prefer the upset pure lead slug, because "what you see is what you get" and it is constant.

[runfiverun]

pound slug.
make a couple of them you'll know which one to use.
and don't forget some type of lube I like lanolin.

[Larry Gibson]

If you know how to use it the Cerrosafe will work fine. I use it all the time. I also have ponded slugs in and they work ok too. Have tried both with the same chamber and got the same results with Cerrosafe a whole lot easier.

Larry Gibson

[LynC2]

If you know how to use it the Cerrosafe will work fine. I use it all the time. I also have ponded slugs in and they work ok too. Have tried both with the same chamber and got the same results with Cerrosafe a whole lot easier.

Larry Gibson

I agree. :D

[aap2]

Thanks guys.

[41 mag fan]

I just did a 45-70 about a month and a half ago. I did the pound slug, and the cerrosafe. The pound slug works great if you're looking for throat size, where your lands start ect.
I did the cerrosafe to look at the chamber also, as the brass wasn't letting me see what I was wanting to look at. Hope that makes sense.

[blackthorn]

An alternative to using Cerrosafe or the pounded slug method is to make either a sulphur or a sulphur/graphite cast. To do this, either use the sulphur ‘as is’, or make up a mixture containing a ratio of approximately two-thirds sulphur to one-third powdered graphite. Sulphur requires a much higher melting temperature than Cerrosafe but it has the advantage of neither growing nor shrinking once the cast has set. As noted, a chamber cast can be made using just sulphur but these casts tend to be somewhat hard to remove and they tend to be brittle. The addition of graphite in the casting makes it less brittle and easier to remove once it is hard.

A container of sulphur can be had cheaply at the garden centre. Clean and degrease the chamber, put a paper plug about one half inch into the rifling, drop a piece of cotton string into the chamber, do not use synthetics, have a wood dowel longer than the barrel and of smaller but as close as possible to the inside diameter on hand. Alternately, you can make a barrel plug out of cork or other stiff material, attach the required cotton string through the plug and push it into the chamber/barrel. Place some sulphur in a small pan with a pour spout, and, using, preferably an electric hot plate, slowly heat the sulphur until it melts, do not let it catch fire, the smoke is () poisonous. Stir in the powdered graphite and pour in enough of the liquid mix to just fill the chamber, wait until the cast is completely hard, this will depend on how large the chamber is, which governs the mass that has to cool down. Carefully push on the cast with the dowel while firmly pulling on the string; it should come out easily once it starts to move.

As noted, unlike Cerrosafe, sulphur cast dimensions of the chamber do not change at all over time, so how soon after casting you measure the cast is not important. Sulphur is one of the few elements that do not change dimensions when going from a liquid to a solid state and will not change shape or dimensions even after many years. Molten sulphur can also be used to set machinery anchor bolts in concrete.

The inclusion of graphite allows the casting to release very easily after it cools. These castings can be remelted for re-use or they can be marked for identification and kept for future reference.