[Jeron Kahyar]

SC if speed is your metric for gauging efficiency why did you bother with the Creedmore?

6.5x55 vs 6.5 Creedmore
156gr Oryx (same for both)

6.5x55:
2352 - 2507 fps

6.5 Creedmore:
2349 - 2536 fps

This gives you anywhere from a 0.1% loss to a 1.1% gain in efficiency. Hardly worth it some may think.

*Just for fun*
300H&H vs 300 Win Mag
180gr Partition (same for both)

300H&H:
2802 - 2939 fps

300 WM:
2914 - 3094 fps

This one gets you from 4 - 5.5% gain. Still looks like not a whole lot but it is something I guess.

*And one more
This is one since it is the original topic of these threads.

6.5CM vs 300 WM
156gr Oryx vs 150gr Partition
(Bullet weight is about as close as you get)

6.5CM:
2349 - 2536 fps

300 WM:
3124 - 3288 fps

Now we can see that jumping to the magnum gives a 23-25% gain in velocity. Now we are getting to something that looks like an actual difference.

*All data from published Norma load data*


Now looking at this seems there is less of a reason to go from the old fashioned cartridge to the new version. Than making the leap from standard chamberings to magnum chamberings. In the end this snipit of information leaves out so much that it is nearly bordering on untruthful. But you know what they say: "There is two kinds of lies damned lies and statistics".