I don't know why I read these threads. I suppose there are some gems within the hyperbole; straw man arguments; knitpicking; and awe and amazement when a person writes that it may not be a good idea to use 6.5CM on the big 5 in Africa (hyperbole intended!)
Generically, I think discussions like this fall into a few traps as we discuss lower charge weight but higher bc cartridges. Here are a few thoughts:
1. A good, on target shot on game can have similar terminal performance as long as the caliber and bullet construction is in the same zip code. We aren't comparing the high velocity grain of rice vs a rainbow trajectory slug (or a similar .224 vs .375.) At least .264, .277, .287, and .308 are reasonably close with what could be similar bullet weight offerings.
2. Bullet construction. This is where some "no free lunch" caveats come into play. Anybody can talk about higher bc with .264 match bullets. There is no argument there. The argument that would come into play would be: does the velocity window for the hunting bullet used match the distance at which game is taken? Additionally, is the additional distance with the higher bc's usable (does it impart enough energy for the bullet to expand appropriately on impact - or does it expand too much)? Also - If higher bc's afford the ability to land a shot at longer distance, does the shooter (and equipment) have the ability to make the shot at that distance?
To think about some of the bullets that could be used for hunting elk:
Nosler ABLR 142gr BC .625
Nosler AB 140gr BC .509
Nosler Partition 140gr BC .490
Hornady ELD-X 143gr BC.625
Woodleigh 140gr PPSN BC .444
Some of these are impressive. But remember, no free lunch.
Even Hornady states the ELD-X has 50-60% weight retention in the 0-400yard range and that this is by design.
https://www.hornady.com/heat-shield#/!/#story
I think I would prefer a higher weight retention for elk, but it is up to the hunter's choice.
Bonded bullets are great for weight retention, but give up some in terms of group size - ie there are no bonded match bullets. Additionally they use dead soft lead and thick plated jackets in manufacturing. Depending on your shot location and distance, you may not get an exit wound.
The partition is absolutely going to perform and give you two holes (as long as it doesn't crack in half - haha), but gives up some in BC (you have to keep those spitzer points from flattening!) and some in accuracy due to the "three part bullet".
The Woodleigh is an incredibly tough bullet, but gives up more in BC.
I'm not using this to rag on all these choices. It's just to say that the "best BC with the best terminal performance" bullet doesn't exist, regardless of what the brass wrapper is. You have to make a choice to the detriment of another factor.
3. One more...the "I need low recoil to practice more" argument. Sure, everyone needs to practice. That isn't at issue. The issue here is knowing the game animal. An elk has a kill zone of approximately 16" (some are bigger/smaller due to the size of the animal). We aren't talking about needing sub moa at ethical ranges here. Also, hunting isn't a lot of shots. It's a lot of waiting for one shot (more if you can get them)...and you're not at a bench or on your shooting mat... and you have to be ready and alert to shoot since the game animal isn't on the hunter's schedule. All that to say - most hunters (or people who shoot regularly) do not need an inordinate amount of practice to hit a 16" target at 400 yards (basically 4moa). If you're trying to go longer on an elk, knowing your hold over isn't enough. A spotter with a wind call is more important at that point.
Maybe I'm just crotchety, but these "low recoil, high bc" hunting threads all seem to go the same way. There are a lot of opinions out there. My main idea is that there are benefits and detriments to choices. There is no wonder caliber and there is more to this story than simply "high bc bullets.) The 6.5CM has detriments too in regard to elk hunting.