Today I am re-reading Jack O'Connor's book, "The Rifle Book", copyright 1964. I found the following quotes about the .243 Winchester cartridge very interesting. Pages 185-187:
"I prefer the .244 (6mm Rem) to the .243. I like the shape of the case better. The powder capacity is greater. The 26-degree shoulder is more adapted to the use of slow-burning powders than the 20-degree shoulder of the .243."
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I know I'm NOT the only one who knows this but, apparently the dis-info is still present.
I've been loading, shooting, and hunting the 243 and 6mm R since the 1980s. I also HAD/have a chronograph to compare loads so what I'm about to say, I have verified and others have too.
As to the powder capacity of the two cartridges, there IS ONLY 1 grain of difference in working, safe loads between them.
As to any velocity diff. there may be 30 fps or NOT depending on the rifle barrels on the individual guns.
The 6mm case LOOKS larger than the 243 because it's longer (taller) but IF you measure the difference of the cases you'll find the 243 is 'fatter' and the 6mm is more slender, therefore the capacities are NOT that different.
As to velocities, I've graphed MANY loads in both cartridges using the SAME powders. The velocities are so close that NO loader/hunter or game could distinguish between them.
Hope this helps, it has been proven.
Jerry
