My understanding is that the only difference between a 5 pin versus 7 pin (I am unaware of any 6 pin offering) is the manner in which the intercepting safety sears are driven. In a 7 pin gun a leaf spring is used, thus driving the requirement for 2 additional pins. In a 5 pin gun a coil spring powers the safety sears, negating the need for the two extra pins.
As noted, the general feeling is that a 5 pin gun is slightly cheaper to manufacture.
If I am incorrect in my understanding I welcome the feedback of those more knowledgeable!
Mike
