All my subsonic loads are now made with Trail boss as it is just so much safer than fast burning pistol or shotgun powder. No chance of a double charge.
Here is some info for 800X and Blue Dot from Calhoon for the 223. I would start with the min load and work up carefully. Near the bottom of the article he talks about loads for the 222.
http://www.jamescalhoon.com/bee.php