Here is a picture of the 64 grain bonded solid base recovered at a modest 2750 fps.
Using my favorite test medium. Two nylon plastic 5 gallon Home Depot buckets filled w water and a plastic lid. Closely duplicates both retained weight and frontal area of bullets fired into cape buffalo. (Nylon is tough and will rip wings off a 458 Barnes X). Also closely duplicates 10 percent IWBA gelatin shots with both pistol and supersonic rifle bullets for penetration.
About 62 grains and uniform .441 caliber.
Cut in two.
Plastic disc is from entrance to second bucket. 22 inches penetration total an inch or so more than a 62 grain Barnes X at 2890 fps.
Spliting front of bucket is rare in the 223. Conventional cup and draw bullets normally require 270 class ctg to do so. This indicates good dwell time of over pressure.
My take on 64 grain is that it is worth the effort to find AR15 friendly load for. Wish Nosler had done so for many Black gun users!