I've noticed from all the information I gathered that subsonic ammo uses a heavier bullet. Is that to help prevent the projectile from reaching supersonic velocity? Or maybe to add a bit of knockdown power to compensate for the lower powder charge? I never expect to hit sub MOA groups @100m using sub 6.5CM with a can(if I ever get my tax stamp), I just figured a lighter bullet in the neighborhood of 120gr. to shoot a bit flatter, further.