I'm wondering what your opinions are on the cannelure. Do you look for it, do you try to avoid it, does it matter, why does or doesn't it matter to you? You get the idea.

It depends on the bullet design. I personally wouldn't go out of my way to look for it. The cannelure is supposed to crimp the lead core in place *I think*. Not all bullets need cannelures though. The cannelure may be detrimental to a bullets function - it all depends on what it's designed for. If you're talking about M193 specifically, then I believe that the cannelure is an integral feature. I don't doubt that you could make a bullet without a cannelure fragment just like M193 if you put your mind to it.

In .223 and AR rifles specifically, I generally prefer loads that have a cannelure if I can get them.

For your viewing pleasure, Hornady 75gr BTHP
[img]http://mysite.verizon.net/~vze1nzcr/ar15/Dscf0023.jpg[/img]

Ammo is with cannelures is required for maximum reliability in self loaders. The cannelure prevents bullet set back on feeding, which will lead to failures to feed, and bullet jump on chambering, which will lead to higher chamber pressures. Cannelures are also an aid to fragmentation as they create a pre stressed portion of the bullet jacket.

Note, I didn't say that I never shoot ammo without cannelures. I did have a fun time one day with some non cannelured 40 grain HPs. I wound up turning my AR into a kinetic bullet puller.

Cannelures, along with staked primers, thicker brass, annealing, and waterproofed case mouths and primers, lead to extremely reliable ammo which in turn leads to extremely reliable weapons. However, those things cost (more) money.