I used 61/2 in. of duct seal, a clay like bar that Electricians use. At 20ft away the bullet did make it 3/4 of the way thorough the duct seal. Then I pulled it apart to find that the top half of the bullet broke up into 1/4 in pieces and the bottom was solid below the crimp groove,and rounded off on the top. I can not account for 36 grains, it must be very small pieces, like dust.I then shot 255g CAS Bullet at it, and it went all the way thorough.So which one would you use for Deer hunting?