If you are comparing the performance of the 6.5CM to the .270 over normal hunting ranges , here are a few points to factor into your calculations:
1. Use a well-constructed hunting bullet that you can shoot through the shoulder of a deer without it blowing up before getting to the vitals, perhaps compare the 140 grain Accubond or TGK in .270 to a similar CM bullet
2. Use a muzzle velocity that a temperature stable powder gives you such as H4350 or H4831sc that will work well at -4 degrees to 100 degrees without significantly affecting your velocity , pressure and point of impact
3. Use the same length barrel 22" to 24"
4. Do not use a 200 yd zero. Sight your .270 in for 3" high at 100 yds and the CM for the same.
5. Use your accurate load of temperature stable powder which gives a moderate pressure, not the exaggerated published loads of factory loaded ammunition, nor maximum load
6. factor in that the .270 has 10 % more cross-sectional area than the 6.5 for a bigger wound channel
7. Give drop figures at 100 (+3"), 200, 300 , 350 yds
8. State what loads, projectile, barrel length you are using
.277 vs .264 is only about 5% larger unexpanded, same if you use 1.5x for expanded differences.
10.24 % difference in cross-sectional area using formula pi x radius squared...... .0547 square inches for 6.5 (.264") v .0603 square inches for .270 Win (.277")
You got me there. Still not enough to make a real difference in wound channel.
Bullet construction/design would make more of a difference but then it's hard to make an apples to apples comparison on that because 1 make/model can be softer/harder or have different jacket thickness in different calibers.
Accubond in .277 140 may expand more or less easily than .264 140 grain Accubond.
Shoot a deer through the shoulders with any hunting bullet in either cartridge and he will be dead in the shadow where he stood at the shot.
It's all just a pissing match.
.264 lovers won't budge and neither will the .277 lovers. Myself I don't have a rifle chambered in either caliber.
Critters on the other hand can't tell 2 fugging bits difference when hit by either one.
