Very good point about will to kill. I have a friend who was in WW2 and I remeber something he told me a while back about the early days of the war. A lot of our fighting force was made up of young Christian men who were raised in rural communities. The all grew up hunting and shooting and were very accurate shots before they ever joined the military.
They scored very highly as riflemen during basic training but when dropped in a war zone they could not hit anything. What they discovered was they had all been trained shooting at round targets and because of their Christian upbringing subconsciously were missing on purpose when firing on another human. That is when they started using human silhouette tagets in training.
As soon as they did accuracy increased dramatically on the battlefield. It is about mind set ad much as it is about caliber and accuracy.