Hello Daryl_S,
Thanks for the reply.

Because the rifle caliber on this Cape Gun is obsolete, and because brass for it is totally non-existent, and because custom loading dies are expensive, and because it would take almost 2 years to get them, and because I shoot "all" of my collectables, well .... I came up with a very simple solution. I rented a 450 bpe reamer for $35, and I hand reamed the 11.6x82R chamber. It took less than 30 minutes because all the reamer did was to remove the sweeping taper in the middle of the chamber. That amounted to only about .010 of an inch. Now the rifle chamber on this Cape Gun is a standard 450 bpe.
The reamer also cut the rim diameter rim thickness to standard dimensions. I already have 2 double rifles, and a single-shot in 450 bpe caliber, and I have reloading dies, and brass, and bullets for them. So ....tomorrow I go to the range for shooting.