Re: strange 30/06 case
I read something about those years ago. I believe if you check the capacity of the case you will find that it is much less than a normal '06. Some were made with an insert inside the case, much like a 30 carbine case, and the annular crimp around the case that you see was place there to keep the insert in proper location. That is probably the meaning of the SPRC...i.e.: "Special Purpose Reduced Charge". Used for small game or harvesting cull animals. I may be disremembering, as it has been 30 years or so since I read that...JMHO