I'm just going to roll my own. I just finished tumbling all the .223 brass I have acquired over the last few months and it filled a Rubbermaid tub 2/3rds full! My machinist buddy in El Paso has everything set up to make 300 BLK brass in a production line kind of way and told me to just bring over whatever I wanted to do on a Saturday afternoon and he would help me knock it out! He'll send me home with it all sized, trimmed and ready to load.
On another note, he got ahold of a bunch of .223 blanks and made 300 BLK brass out of it! He dumped the powder and formed the brass without removing the primers and is using it for subsonic loads. He said that the primers are kind of soft, like pistol primers but they work good. The blank brass has a cannelure around the case near the base, which is another reason he only uses the brass for subsonic loads, but he can tell at a glance whether the round is a subsonic or supersonic load.