I just bought a number of bullets. 100 grain spire point with the cannelure. What purpose does the cannelure serve and if I load the 243 to nearly 2.710 it is nowhere near the cannelure mark on the bullets. Should I load the bullets down next to the cannelure? I am not planning on crimping the bullets.
I switched to Imr 4831 and the 243 in Rem 742 is beginning to shoot better groups. This is in answer to the question that I asked the other day when I posted that I could not get the Rem 742 to group. Thanks

JUST LOAD NORMALLY. the cannalure does not matter.
Only if you crimp.

I think its just to hold the lead to the jacket on impact, a crimp on the outside also produces a ridge on the inside of the jacket. I load no where near the crimp on the bullet, I keep my bullets about .015 off the lands.

Ignore the cannelure, load to the length that groups the best.

what jstevens said.

The cannelure on the bullet is for crimping. This is done to keep the bullet in place. Bullets can move foreward or be seated deeper under various circumstances. It is not designed to be a reference for seating depth.

As has been said the cannelure is for crimping, but in reloading it is usually in the wrong place, so most people simply ignore it. I do think that Hornady for instance uses it as the "interlock" to form a ring inside the jacket to hold the lead core from moving forward upon impact, thus keeping the bullet in one piece. You need not concern yourself with it, even if you want to crimp, use a Lee factory crimp die and crimp anywhere on the bullet you like. If it happens by coinsidence, that the cannelure is in the right place, simply crimp with a normal seater die. Most people I know don't crimp at all. But, I've been playing with a Lee factory crimp die in .270 and it does seem to close the groups up, very slightly. I'm seeing a difference, but it is slight. I haven't tested it a lot but the ones I've tried, show about a 1/4" improvement at 100 yards. The trouble is the rounds without the crimp group in the 3/8" or less range, and I'm not sure I'm able to shoot smaller groups with a 3-9X scope. The groups that end up being one hole, could simply be a good load with good luck shooting.