I would also highly recommend you get QuickLoad as it will show a lot of things that people can't see any other way.
This is a sample chart of a mild load in 264 Win Mag. It shows % of combustion for barrel length. You can see that all of the powder is not burned up until the bullet has traveled 16"-17". You can play with it and change powders, loads etc. and see that some loads never burn all of the powder in a given barrel length.
If you do the same for chamber pressure vs. bullet travel you will get this. Interesting huh? You can see that in this instance the max chamber pressure doesn't start to drop until the bullet has traveled 3"-4". Looks like, in this instance, the bullet would be into the rifling/barrel a few inches before peak pressure exists. That would mean that the gas burning behind the bullet at peak pressures would be "attacking" the throat.