Rotometals Chamber Alloy (158-190) is the best known material from which to make a casting of the chamber and throat of a firearm to determine caliber or check the dimensions. It melts at a temperature just above M & M's, so all you need is a propane torch and a bullet casting ladle. It can also be used to make a cast of a dovetail slot or any other hard to measure area. Also, it is great for removing the front half of a case from the chamber, in the event of case head separation; and lots of folks cast a small portion of the barrel to determine bore diameter. For best results, measure the casting one hour after casting. Contains 42.5% Bismuth, 8.5% cadmium, 37.7% lead, 11.3% Tin.
Sold by the ingot. Ingot weighs approximately 1 pound.
- Plug the bore immediately ahead of the throat of the chamber using a small cleaning patch.
- Pour the alloy directly into the chamber until full and allow Melting Point to cool, it will turn a shiny silver color. As soon as it has cooled enough that it is no longer a liquid (and doesn't present a burn hazard), remove it from the chamber. Take care not to overfill the chamber as the alloy will then run into the locking lug area, making removal extremely difficult.
- During the first 30 minutes of cooling cerrosafe shrinks. At the end of one hour it should be "exactly" chamber size.
- Melts between 158 and 190 degrees Fahrenheit
- Should be melted in a clean iron ladle without direct flame on the product.
- The chamber being cast should be cleaned thoroughly and a thin coat of oil or graphite applied.
Contraction expansion factor versus time, measured in inch per inch compared to cold mold dimensions. Test Bar x 10
- 2 minutes - .0004"
- 6 minutes - .0007"
- 30 minutes - .0009"
- 1 hour + .0000"
- 2 hours + .0016"
- 5 hours + .0018"
- 7 hours + .0019"
- 10 hours + .0019"
- 24 hours + .0022"
- 96 hours + .0025"
- 200 hours + .0025"
- 500 hours + .0025"