This is something that Dennis at Stream Systems that make the "Hot Shot" and I have been working on for quite some time. Don't know how to explain it without a lot of theory and electronic jargon but the tin is shielding the iron and the tungsten from the unit. Nice Shot registers in the Hot Shot until it is run through the furnace, then it doesn't.
Anyway we have been using magnets to prove that it is Nice Shot. The older shot that was manufactured for me needed this magnet
http://www.amazingmagnets.com/show-frac ... e-n42.aspx These are rare earth magnets, the same needed for the tungsten-bronze shot that is out there.
I have been able to increase the magnetism of the Nice Shot I am making here but the Hot Shot doesn't seem to like the quantity of tin in the shot. I'm not saying anything bad about the Hot Shot either, it is a good product and Dennis knows the frustrations involved with the newer shot compositions.
In short, if you use the magnet listed above there should be no doubts about Nice Shot.
PS, Don't get that magnet near any magnetic storage device.