I used Accubonds in Africa and have killed a couple of whitetail with them. 150 and 180 grain out of a .30-06. My big fear was losing (and paying for) one of the big animals in Africa but I bang-flopped a 600+lbs wildebeest and my zebra went lest than 20 yards. If I go back, I'll taking Accubonds again. This is the one dug out of my zebra - it was just under the skin on the opposite side and a zebra has skin that's about 3/8" thick.
I have shot probably 8 elk with a 270 win. and Nosler accubonds. 130s. All cows. Shot 1 bull with the .270 because my 30 cal.with 180s had broke down. No problems but I accepted the fact I could not get sloppy with shot placement. Never used a 6.5 on elk but with well constructed bullets I don’t see it being an issue. The problem with the 150 core lok, is it is designed to shoot lighter thin skinned game like deer. At high velocity it will show its shortcomings sooner as it will be more inclined to deconstruct before it can get to the vitals. IMO, if you want to go 150s you need a tougher bullet. Most 180s in 30 cal, cup and core are of tougher construction than the 150 class cup and core. Use a bonded bullet or one with more robust construction and you can go lighter if you prefer.I wonder what size bullet the 270 and 6.5 advocates are shooting?