[tkglazie]

You've already gotten lots of good ideas, and I'd echo some of what has been said. I'd add in terms of pros that generally speaking a longer COAL is going to give better accuracy, because by getting the bullet closer to the lands it's going to also engage the rifling more concentrically. At the same time, too long will put you into the lands which is can be dangerous in terms of creating a pressure spike. So what manuals do is provide a COAL that will typically be safe in all rifles, but not one necessarily that's ideal for any given rifle.

So it's helpful to find how long you can go in your specific rifle. As mentioned, anything magazine fed will have a max length that's going to fit into the magazine, and sometimes that magazine length will be as long as you can go. Other times a mag will still allow you to seat out long enough to get to the lands, and if so I find my best accuracy is generally .010-.015" off the lands.

Wow. Those two paragraphs are about as well written as any I have read on the subject. Well said.