"I have seen one hundred men who would call themselves Masters yet if you took all their skills added together, you would not have the makings of three good students, let alone one Master…of this art there are few Masters in the world"- Master Fiore dei Liberi, Flos Duellatorum, 1410
The quote above is 600 years old and is about swordsmanship. Unfortunately, not much has changed. In the field of marksmanship it has worsened.
How do you determine if someone truly is a master at marksmanship and worthy to teach? Jeff Cooper laid out the following criterion which remains the best I've seen to date.
What does it take to be a Master of Weaponcraft?
First, it requires demonstrated expertise with the chosen weapon. A master need not be a world champion in competition, but he does need to be a dangerous competitor. He must be able to do everything that the weapon is capable of doing, and doing it on demand. He must be able to show his students exactly what is expected of them, while not, at the same time, intimidating them.
Second, the master must understand the theory of the technique of his instrument. He must know the geometry and physiology behind the shooting process. Generations of military and police instructors have got by without this by simply emphasizing "This is the way we do it!" While that may be good enough for government work, it is not the best way to success. I remember from long years ago an encounter with a great master of the saber. We youngsters depended almost entirely upon speed, but this gentleman showed us that speed was unimportant without timing. To demonstrate he would choose a pupil and than say exactly how and where he would hit him - and then do it. When your master can do that to you, you tend to believe what he says.
Third, the master must have a genuine desire to impart. Here is where the master differs from the mere expert. He must desire excellence in his students more than excellence in himself, and seek at all times to produce that. We have all known some very good shots who have failed as teachers because of a lack of this essential desire.
Fourth, the master demonstrates "command presence," which is a combination of articulation, vocal tone, posture, and attitude. The master must be able to command without rank. Obviously, true masters of weaponcraft are not common. During the time I ran the school at Gunsite, I sought continually for people who displayed the necessary qualifications, but I did not find a lot of people who made the grade. That is doubtless one reason why really good marksmanship is so rare. Very few practitioners are truly qualified to teach it.