Well, way back when ebay sold once fired cases, I found a seller that was getting a lot of 10mm from a police practice range. After that on another board I got into a group buy for 500 new Starline nickel plated 10mm cases. 40 cal is always easy to find at the range and pick up for free, I have never bought any brass for it. I use the exact same 185 grain Precision Bullets for both calibers.
I also got lucky and bought out somebody's Lapua cases for 7.62X54R. And for a while I had a Lapua distributor selling them for $30/100, and I snarfed up about 600 cases. I loves to find deals on cases.
