In the 60's, Sierra had their factory about 15 miles east of Los Angles. On the street in front of the factory, they had a little old 2 bedroom house that was painted Sierra green that they used as their 2nds store. They were not called blems then. On the walls were 2x4 racks with with wooden bins with the bullets that were available, There were metal scopes and paper bags and you just filled the bags with the amount that you wanted.
Have you been to their factory which is now in Vandalia, MO? They have one area where they have their blems for sale and it is filled with 35(?) gallon drums, each one containing a different bullet type. You're not allowed to get your own any longer but an employee will get what you need. Some bullet types aren't priced all that cheaply, but you can find some deals depending on what you need.