What do you think this is the Army, where you shoot'em a mile away?
I love how Michael barely reacts to this line from Sonny. And how ignorant it shows his brother to be.
I wonder if Coppola had his druthers when making this movie he might have included a flashback to Michael's service with the Marines at Guadalcanal and Peleliu. The fighting Michael experienced there was some of the worst in the entire war. It was just about everything BUT shooting the enemy from a mile away. It was up close and personal. Often hand to hand. Way, way worse than just about any of the mob hits that are depicted in these movies.
The irony is that much of the combat Michael saw was pretty much the way Sonny described it. With the enemy's brains splattered all over his dungarees.