The rules for Called Shots changed back in Rogue Trader, making Called Shots into a Full Action iánd a Hard BS/WS test instead of just a -20 modifier to any attack made.
I never really liked this change, but now with BC it goes even further because you do not get the +10 bonus given to Standard Attacks.
How come I can make an aimed shot at a servo skull at my regular BS, but If I try to hit the head of the fellow standing next to him I don't have time to Aim, and get a -20 penalty?
Selecting the right tool for the job doesn't really help either, but illustrates the "problem" nicely. Lets say you have an Accurate weapon, and take a Half Action Aim before shooting at the Servo-skull. A Head-sized target buzzing around at normal range, it modifies the shot with a -20 penalty.
Aiming with an accurate weapon gives a +20 bonus, and the Standard Attack another +10. So your net chance to hit the little skull is BS +10.
Now attach the skull to a body, and all of the sudden the same shot becomes a Hard BS test, requiring a full action so no time to Aim. It's suddenly much harder to hit the "same" target.
I'm considering just keeping the DH version. What have you done with Called Shots?