Here is a picture i just took, The bullet on the left is my REALLY HARD 15 BHN, Bullet on the Right is Pure Lead or Close to it. What this picture is tended to show is the Sprue cuts, Notice the Sprue cut on the Pure lead bullet on the right, it is more of a Smear Cut (my Certified 40:1, 8.5 BHN stil does this EXACT same thing)
Now notice the bullet on the left, it has little holes, More like a Tear. In my experience i have found this starts happening in the 9.5-10 BHN range. This is decent indicator to go by, It’s not gonna give you the precise BHN, But you can definitely determine if a bullet is Soft, or up to around 8.5 BHN if the Sprue is a Smear type Cut, If the Sprue is more of a Tear, with tiny pin looking holes, You can be certain they are Fairly Hard
