If you are not seeing a difference in group sizes from one test load to another, something is off. It could be many things. Most common is the OAL is too short and you are jumping the bullet too far to see where the rifle is really wanting the bullet at a certain velocity. Another can be the gun just doesn't like the bullet. Neither of my 308's shoot 150's for damn. They both shoot 175 SKMs in half inch groups. Barnes bullets are a PITA if you ask me. They are long and light, and this makes everything kind of a craps-shoot like Steve was mentioning earlier.