R R - I'm not mad, just tired so this is my last response.
1. You ask how is s d more relevant than weight.
That is the reason you & others don't understand the reality.
The s d is the ratio of dia/length and with the same nose shape, bullets with similar s ds are proportional.
When you compare 130 wt between 264 & 270, you're NOT comparing proportional bullets. (apples/oranges) A 130 264 is more aerodynamic than a 130 270 BUT is COMPARABLE to a 140 270.
2. AS any bullet's s d increases velocity decreases in the same cart. The 6.5 loses TOOO.
3. B Cs are only accurate indicators when used with bullets of similar S D. (comparable)
THUS using 264 120 gr IS comparable to 270 130 gr.
and 264 130 IS comparable to 270 140 gr.
I don't know your reloading background and I'm NOT being critical, but this lack of understanding is the reason you don't understand the REAL relationship between the 260 & 270.
We have writers here on the fire that can explain this better than I. And they do understand.
No hard feelings. I am buying a 6.5X55 and keeping my 270s.
Happy Thanksgiving
