Saw a video where a guy pulled bullets off of some 7.62x39 and removed some of the powder and seated bullet again to make a subsonic round. Did he just trial and error this or is it a common practice that is safe and tested somewhere?
Could be pretty dangerous.. Most powders have a minimum fill in the case.
Powders like H4895 can be reduced quite a ways.
Get too low of powder charge and you will get a hangfire. or where the primer shoves the round into the lands and then the powder starts burning and causes a high pressure issue because the lodged bullet.