Lama bob,
I read your posts in this thread with interest. You seem to have a solid take on pressures and load procedure for the 3 - 7mm's in this discussion.
Your figures on velocity differences and case design between them seem in line with your testing and beyond my ability to confirm or dispute, I do think you know what you're talking about.
However, in the real world of "joe average" we go by published load data that has been pressure tested by people that do make public their data.
This published data shows a real world difference in cartridge velocities as shown by the data Muledeer posted in this thread.
For me and most other reloaders who don't have our own piezo equipment or a laser vibrometer available, published data and a chronograph are the best we have.
So for now I guess that the data I use has been tested and accepted for common usage and the postulation you've made is just an opinion, Although interesting - still just your opinion.
I'm certainly not going to argue with someone using whatever load data they want. The reality is that there's a lot of it out there, and the average quality is very bad. If you think the data's been pressure tested in a way that will prevent an over-pressure situation (like you might expect with factory ammo) you'll be disappointed. Most of it hasn't been pressure tested at all other than not having blown up someone's rifle somewhere. Some of it (for example the Berger book) is 100% "dry labbed" - it's never even seen the inside of one rifle, just simulation software. Data listed in CUP (like most of the Weatherby data) is probably +-10% once you convert it to useful pressure units. Piezo data is sometimes better. Then of course there's the data where the lawyers told them to lower the charge weight, and they left the velocity and pressure where it was (Hodgdon, I'm looking at you...) thus baffling anyone which a chrono and/or strain gauge that tries to use it.
Given the general mess, I roll my own. But if people want to use a specific cartridge because it has high pressure/velocity data published for it (and that's generally true for the Weatherby cartridges - often over pressure) then I can understand that.
