I use these bullets in several handguns and rifles and the forward cannelure is for 92 rifles whose COAL is shorter than the cylinder lengths on my Super Blackhawks, sorry have never used 2400 so I can't comment there, always have used Win 296.
I always start with mid range book loads and work up until the case doesn't fall out of the cyl by itself, just needs a slight tap. This is safe and is usually a lot higher than book max, but where you feel comfortable is up to you.