As far as I know, AAC doesn't make a piston with a 5/8-24 thread pitch, probably because they don't want people using TiRant 45 suppressors on 300BLK since they aren't rated for the use of supersonic ammo on that caliber. AAC does not recommend using the TiRant cans on 300BLK in case someone accidentally runs supersonic ammo through it and damages the can, themselves, etc.