The points that the OP should really be arguing are that in the same case, e.g. 6.5-06 v .270 Win, the .270 will usually drive the same weight projectile (e.g. 140 grains) faster. This, together with a larger frontal area will give the .270 a slight advantage at most normal hunting distances, provided the sectional density is sufficient for complete penetration (which it usually is). Eventually the higher bc 6.5 projectile will catch up and be superior at the extreme distances. If 99% of shots my most hunters are taken at the shorter distances, then the .270 has some advantages over the 6.5. For the occasional shot at 600 yards, it doesn't really matter that there may be better options than a .270, a .270 will still be ok. Practicing at 600 yards with a .270 Win or .270 PRC is still a beneficial exercise, knowing full-well that 600 yard shots are in the minority and that the .270 really shines at the more-frequent closer hunting ranges.
The major problem with your "theory" is that there's far less difference between how various "cartridges" (actually bullets) kill big game than many hunters believe. This is especially true of "frontal area," which is only minutely different between 6.5mm and .270 bullets--and doesn't matter nearly as much as EXPANDED bullet diameter, which can vary considerably with various bullet designs. Some bullets expand far more than others, in particular bonded bullets--but this also reduces penetration, because the major factor in penetration is NOT retained bullet weight, but frontal area.
I have considerable experience with the .270 Winchester on big game, partly through buying my first in 1974, and after a couple of decades having used it on more big game than any other cartridge. Plus, my wife got her first .270 in 1984, and killed a bunch of big game with it as well, at one point making 10 one-shot kills in a row on animals, from pronghorns at over 400 yards to bull elk and moose.
I have also killed quite a bit of big game in the same size-range with various 6.5mm cartridges, and seen hunting partners do the same, including the 6.5 Creedmoor, 260 Remington and 6.5x55, which produce basically the same velocities with the same bullet weights. I have yet to be able to tell ANY consistent difference between the way any of those 6.5s (and several others) kill big game and how the .270 Winchester kills big game.
This is partly because there's actually far less difference in how various "cartridges" (again, actually bullets) kill big game as long the bullet penetrates and expand sufficiently while passing through the vitals.
If you prefer to believe in such minute theoretical differences as .013 in unexpanded bullet diameter in "killing power," that's your privilege. But I quite believing in such tiny stuff years ago.
The problem with a theory that there is no difference between 6.5 and .270 bullet killing performance as opposed to what I advocated being a slight difference, is that the same argument becomes there is no difference between .270 and 7mm, and no difference between 7mm and .308 in killing performance. Similarly, there is no difference between .308 and .338, and no difference between .338 and .375. Therefore, there is no difference between the killing power of 6.5 and .375. Now obviously there is a difference between 6.5 and .375 killing power. A better theory is that the difference between the killing power of 6.5 and .270 is only slight - which is what I said. I agree, that it is usually not noticeable, but this is probably due to the fact that we are unable to duplicate in a controlled scientific way where all other things are kept constant as much as possible, the kills of a 6.5 v .270 in a large enough sample size. I don't really think we are arguing different things, I mentioned "slight advantage" which you didn't agree with, implying there is no difference. However, it seems that your argument is negligible difference versus my "slight difference". I also agree that expanded bullet diameter is far more important than unexpanded diameter, but I haven't seen data which clearly shows that 6.5 bullets expand greater than .270 bullets from the same type of bullet made by the same manufacturer. Even if a 6.5 bullet expands to the same diameter as a .270 bullet of the same weight, then if the .270 bullet is travelling faster, I would expect that it would penetrate deeper simply because of greater momentum brought about by a slightly higher velocity...which is another point I made when I said the .270 bullet has a slight advantage over the 6.5-06 at most normal hunting distances. But I did qualify what I said by using the word "slight".
Generally speaking, I'm in agreement with this.
I'm not commenting on "long range shooting", as I've only had less than a handful of opportunities where that could have been a possibility on a bull moose in the "Far North" of Ontario in some clear cuts. So I toted my .340 Wby for such a possible chance - but ended up shooting a bull at 165 yards. My comment has particular reference to any distinctions in calibers and their bullets in construction and profile.
From 2006 to 2015, I along with one and sometimes two partners were hunting bear on a private properety - an old farm that was no longer in use as such, but hunted for deer by the owner and family. He wanted "all the bears gone"! He was into heavy equipment. During that period we hunted parts of six fall seasons. Two of the bears I shot were in 2011 and 2013. They were shot from the same ladder stand in a line of trees that separated two pastures of uncut grass that was from 24" to 30" in height. The property bordered a Provincial wildlife sanctuary, so lots of game spilled onto this ancient farm. In 2011 my stand was facing NE and in 2013 it faced SE. The two bears were as near identical as twins could be, and both were shot under the chin as they faced me in the tall grass just a few yards from their baits. The range of the first was 70 yards ands the second was 68 yards. They both squared 6'.
Here's the point: The first (in 2011) was flattened on the spot so fast that I lost sight of him in the tall grass. He was shot with a 465gr FT, .458-cal hardcast leaving the muzzle of my NEF single-shot .45-70 at 1900 fps. Impact was about 1750 fps/3163 ft-lbs. The second (in 2013) was also shot as it faced me in tall grass at 68 yards off to the side of the bait barrel. It too dropped so quickly I lost sight of it. I fully expected it to be found where it was hit. I got down from my stand, walked to where I expected to find a dead bear... Instead, no bear was to be found. My partner (a CO) heard the shot from 3 kms away at another site, called me on his radio asking if that was my shot and did I need any help? I replied: I hadn't yet found the bear. That bear was found at the bottom of a nearby escarpment - and what a task for both of us in retrieving it up out of there!
As said, it was a near identical bear to the one in 2011, shot identically under the chin (as all I could see in both instances were their heads and part of their shoulders above the tall grass.
The bullet from the first bear was lost somewhere in the soil under the bear as it left a bullet-size entry in frontal chest and exit below the sternum. When I opened the chest the heart had exploded and the chest cavity was like a pond of blood. There were no fragments of lead, and no evidence that the 465gr hardcast had expanded.
The bullet that killed the second bear was retrieved in the right flank in skinning. It weighed 73% of its unfired weight. A 286gr Partition at +2600 fps and impact at ~2500 fps/3970 ft-lbs from my 9.3 x 62. Not much distinction in KE but a very significant difference in results, which confirms my view that momentum (bullet weight x velocity), bullet caliber, construction and profile can make huge differences in results at "normal" hunting ranges.
Bob
www.bigbores.ca
