The experimenting is called the 12GA From Hell.
There are 2.5 year long threads on it on The Highroad
and Firingline Forums.and many others.It is a long brass 12 ga case
we setup in strong guns for great velocity, like 600gr hard lead slugs
at 2600 or more fps.Here is pic of case next to regular length 12ga plastic
case, and the plastic still fires in smae chamber. It is just a modern
version of the African 12ga paradox guns. Second pic is my
Savage 210 bolt action with heavy barrel chambered for it.Ed