Mike,
You obviously "have it licked", so I'm not trying to get you to change anything, I just find the conversation interesting. First of all, by "bore" do you mean bore or groove diameter? I don't know if the case wall thickness in a 24-bore rifle cartridge case is the same as the wall thickness in a 24 bore shotshell brass case. I'm in the minority, in preferring "nitro for black" loads in my old rifles (not to avoid cleaning barrels, but to avoid having damage internally, due to gases getting inside) and I have to expand the skirts of 58 caliber Mini bullets in order to have enough resistance for the smokeless powder to burn in my 577 Snider. I understand yours and mine are two different cartridges but that is my only experience with 577s. My friends also laugh when I wrap a thin piece of duct tape around a factory 577 Snider case head to insure even expansion. I also find that oversize bullets are not nearly the problem most people think they are, especially cast or swaged ones. If there is a harmful pressure rise, it is because case can't expand to release the bullet. This could be caused by overly long case jammed into the leade as well as the overall diameter of bullet and case preventing release. If the bullet is moving, the volume of the area the gases are expanding into is also increasing thereby mitigating the pressure rise. It is almost like a single stroke internal combustion bullet sizer. The oversize bullet condition can't last any longer than the time it takes for the straight shank of the bullet to move its own length through the barrel. (It is surprising how many people seem to think that a bullet with an outside diameter greater than the inside diameter of a barrel can travel through that barrel and still be larger than the barrel when it exits.) The theory also works with jacketed bullets, except it is easier to jam a jacketed bullet into a case hard enough that the case fails before the bullet starts moving. I often use bullets larger than the barrel's groove diameter (even jacketed, mostly 32/8mm, when conditions allow), but this is still not a "free lunch" because is pretty easy to wind up with a safe load that won't shoot an acceptable group. Then you have to find out whether it is the bullet or something else that causes the problem. Maybe a discussion for a different time would be cases where the barrel demands a bullet diameter larger than will chamber when seated in a case.
Mike