A stovepipe is usually caused by the shell hitting the ejector (the little thing sticking up with the finger forward on the bottom of the bolt chamber) while not being in the grip of the extractor. The shell just turns sideways instead of being flipped out the ejection port. When the extractor is holding the shell and it hits the ejector, its kinda like a tiddlywink effect to spring it out. If its not being held, then it doesn't hit the ejector correctly and it turns up. Thats why the exact edge extractor solves the problem, it holds the shell. The Ruger factory one has a much smaller edge to grab the shell. Once it wears or breaks, its time for a new one. And yes, some ammo will cause more stovepipes than others.