I have a nice one that I purchased through Gunbroker.com back in 2003. It never occurred to me that it is a rare chambering - uncommon, perhaps, but not rare. Mine is accurate and, like all of my BLRs, a joy to handle in the field.
A co-worker of mine has one in 284 winchester - I've have only heard of one other in that caliber and would probably consider it to be a rare one.
Enjoy that BLR!
1977 .358 BLR
1980 .358 BLR - original owner
1987 .243 '81 BLR
1991 7mm-08 '81 BLR