Now this could be an interesting hypothesis....? If I look at a twist rate of somewhere in the 8 or 9 inch range then a moderate velocity will still "take" the twist, but speed it up a bit? Perhaps the "64" starts to jump lands in the heavier loads???

I know that there are many variables. I have a little shooting range on my plot and I see a lot of different issues. I find a common problem is "sporterised" old 303s that just don't group. I know many older barrels had a tighter twist for the older, slower military (cordite?) cartridges. They tend to "strip their moer" as we say in Afrikaans. Is the same not happening with the 7 X 64? Speed it up and strip over the lands?

I have limited knowledge of the "64" but I know it works! That's clear from it's advocates. But the fact is the "57" has NO detractors! There has to be a logical explanation. The only reference I have to twist rate is GS Custom which reflects the same twist rate for both. The "57" is a proven accuracy winner (It always scores well in our PMP comp and many other references swear to it's accuracy) The "64" on the other hand has very few champions. Why? I'm sure it's just more "fussy" but when you hit the right recipe it's great.

I'm not saying I know the answer, but the 7 x 57 works, and the 7 x 64 works sometimes!